python: publish sphinx docs to read the docs

Background:

This is a follow-up to the PR that adds sphinx docs.

Read the Docs is a hosting platform for documentation, primarily Python
docs. It supports builds at commit time as well as at specific git
labels to support versioned docs. I have claimed the
protobuf.readthedocs.io project and can add any Googlers who need access
to be able to configure and trigger builds.
https://readthedocs.org/projects/protobuf/builds/ It's also relatively
easy to create a new project to test the documentation builds from a
fork, such as https://readthedocs.org/projects/tswast-protobuf/builds/

About this change:

Once web hooks are configured, Read the Docs will automatically build
the docs for the latest changes on the master branch.

I needed to update `python/setup.py` to support installation from the
root of the repository because Read the Docs does not `cd python` before
installing the protobuf package with `setup.py install`. To support
this, I updated the file paths to use the absolute path to files. The
`__file__` special variable comes in handy for this, as it provides the
path to the `setup.py` file.

A banner is added to the docs when published to readthedocs. This links
to the official documentation and the future home of the stable API
reference on googleapis.dev.

.readthedocs.yml

@@ -0,0 +1,22 @@
+# .readthedocs.yml
+# Read the Docs configuration file
+# See https://docs.readthedocs.io/en/stable/config-file/v2.html for details
+
+# Required
+version: 2
+
+sphinx:
+  configuration: python/docs/conf.py
+  fail_on_warning: false
+
+# Setup build requirements for docs.
+# Use conda so that we can install the latest libprotobuf package without
+# having to build from scratch just for docs builds.
+conda:
+  environment: python/docs/environment.yml
+
+python:
+  version: 3.7
+  install:
+    - method: setuptools
+      path: python

python/docs/conf.py

@@ -41,7 +41,7 @@
 # add these directories to sys.path here. If the directory is relative to the
 # documentation root, use os.path.abspath to make it absolute, like shown here.
 #
-# import os
+import os
 # import sys
 # sys.path.insert(0, os.path.abspath('.'))
 import google.protobuf
@@ -69,6 +69,7 @@ release = google.protobuf.__version__
 # ones.
 extensions = [
   "sphinx.ext.autosummary",
+  "sphinx.ext.ifconfig",
   "sphinx.ext.intersphinx",
   "sphinxcontrib.napoleon",
 ]
@@ -237,3 +238,17 @@ autosummary_generate = True
 
 # Example configuration for intersphinx: refer to the Python standard library.
 intersphinx_mapping = {"https://docs.python.org/": None}
+
+# -- Config values -----------------------------------------------------------
+# The setup() function is needed to add configuration values to the Sphinx
+# builder. We use this to show a banner when built on Read the Docs.
+# https://www.sphinx-doc.org/en/master/usage/extensions/ifconfig.html
+
+def setup(app):
+  app.add_config_value(
+    "build_env",
+    # Read the Docs sets a READTHEDOCS environment during builds.
+    # https://docs.readthedocs.io/en/stable/builds.html#build-environment
+    "readthedocs" if os.getenv("READTHEDOCS") else "",
+    "env"
+  )

python/docs/generate_docs.py

@@ -95,6 +95,18 @@ TOC_TEMPLATE = """.. START REFTOC, generated by generate_docs.py.
 
 AUTOMODULE_TEMPLATE = """.. DO NOT EDIT, generated by generate_docs.py.
 
+.. ifconfig:: build_env == 'readthedocs'
+
+   .. warning::
+
+      You are reading the documentation for the `latest committed changes
+      <https://github.com/protocolbuffers/protobuf/tree/master/python>`_ of
+      the `Protocol Buffers package for Python
+      <https://developers.google.com/protocol-buffers/docs/pythontutorial>`_.
+      Some features may not yet be released. Read the documentation for the
+      latest released package at `googleapis.dev
+      <https://googleapis.dev/python/protobuf/latest/>`_.
+
 {module}
 {underline}
 

python/docs/google/protobuf.rst

@@ -1,5 +1,17 @@
 .. DO NOT EDIT, generated by generate_docs.py.
 
+.. ifconfig:: build_env == 'readthedocs'
+
+   .. warning::
+
+      You are reading the documentation for the `latest committed changes
+      <https://github.com/protocolbuffers/protobuf/tree/master/python>`_ of
+      the `Protocol Buffers package for Python
+      <https://developers.google.com/protocol-buffers/docs/pythontutorial>`_.
+      Some features may not yet be released. Read the documentation for the
+      latest released package at `googleapis.dev
+      <https://googleapis.dev/python/protobuf/latest/>`_.
+
 google.protobuf
 ===============
 

python/docs/google/protobuf/any_pb2.rst

@@ -1,5 +1,17 @@
 .. DO NOT EDIT, generated by generate_docs.py.
 
+.. ifconfig:: build_env == 'readthedocs'
+
+   .. warning::
+
+      You are reading the documentation for the `latest committed changes
+      <https://github.com/protocolbuffers/protobuf/tree/master/python>`_ of
+      the `Protocol Buffers package for Python
+      <https://developers.google.com/protocol-buffers/docs/pythontutorial>`_.
+      Some features may not yet be released. Read the documentation for the
+      latest released package at `googleapis.dev
+      <https://googleapis.dev/python/protobuf/latest/>`_.
+
 google.protobuf.any_pb2
 =======================
 

python/docs/google/protobuf/descriptor.rst

@@ -1,5 +1,17 @@
 .. DO NOT EDIT, generated by generate_docs.py.
 
+.. ifconfig:: build_env == 'readthedocs'
+
+   .. warning::
+
+      You are reading the documentation for the `latest committed changes
+      <https://github.com/protocolbuffers/protobuf/tree/master/python>`_ of
+      the `Protocol Buffers package for Python
+      <https://developers.google.com/protocol-buffers/docs/pythontutorial>`_.
+      Some features may not yet be released. Read the documentation for the
+      latest released package at `googleapis.dev
+      <https://googleapis.dev/python/protobuf/latest/>`_.
+
 google.protobuf.descriptor
 ==========================
 

python/docs/google/protobuf/descriptor_database.rst

@@ -1,5 +1,17 @@
 .. DO NOT EDIT, generated by generate_docs.py.
 
+.. ifconfig:: build_env == 'readthedocs'
+
+   .. warning::
+
+      You are reading the documentation for the `latest committed changes
+      <https://github.com/protocolbuffers/protobuf/tree/master/python>`_ of
+      the `Protocol Buffers package for Python
+      <https://developers.google.com/protocol-buffers/docs/pythontutorial>`_.
+      Some features may not yet be released. Read the documentation for the
+      latest released package at `googleapis.dev
+      <https://googleapis.dev/python/protobuf/latest/>`_.
+
 google.protobuf.descriptor_database
 ===================================
 

python/docs/google/protobuf/descriptor_pb2.rst

@@ -1,5 +1,17 @@
 .. DO NOT EDIT, generated by generate_docs.py.
 
+.. ifconfig:: build_env == 'readthedocs'
+
+   .. warning::
+
+      You are reading the documentation for the `latest committed changes
+      <https://github.com/protocolbuffers/protobuf/tree/master/python>`_ of
+      the `Protocol Buffers package for Python
+      <https://developers.google.com/protocol-buffers/docs/pythontutorial>`_.
+      Some features may not yet be released. Read the documentation for the
+      latest released package at `googleapis.dev
+      <https://googleapis.dev/python/protobuf/latest/>`_.
+
 google.protobuf.descriptor_pb2
 ==============================
 

python/docs/google/protobuf/descriptor_pool.rst

@@ -1,5 +1,17 @@
 .. DO NOT EDIT, generated by generate_docs.py.
 
+.. ifconfig:: build_env == 'readthedocs'
+
+   .. warning::
+
+      You are reading the documentation for the `latest committed changes
+      <https://github.com/protocolbuffers/protobuf/tree/master/python>`_ of
+      the `Protocol Buffers package for Python
+      <https://developers.google.com/protocol-buffers/docs/pythontutorial>`_.
+      Some features may not yet be released. Read the documentation for the
+      latest released package at `googleapis.dev
+      <https://googleapis.dev/python/protobuf/latest/>`_.
+
 google.protobuf.descriptor_pool
 ===============================
 

python/docs/google/protobuf/duration_pb2.rst

@@ -1,5 +1,17 @@
 .. DO NOT EDIT, generated by generate_docs.py.
 
+.. ifconfig:: build_env == 'readthedocs'
+
+   .. warning::
+
+      You are reading the documentation for the `latest committed changes
+      <https://github.com/protocolbuffers/protobuf/tree/master/python>`_ of
+      the `Protocol Buffers package for Python
+      <https://developers.google.com/protocol-buffers/docs/pythontutorial>`_.
+      Some features may not yet be released. Read the documentation for the
+      latest released package at `googleapis.dev
+      <https://googleapis.dev/python/protobuf/latest/>`_.
+
 google.protobuf.duration_pb2
 ============================
 

python/docs/google/protobuf/empty_pb2.rst

@@ -1,5 +1,17 @@
 .. DO NOT EDIT, generated by generate_docs.py.
 
+.. ifconfig:: build_env == 'readthedocs'
+
+   .. warning::
+
+      You are reading the documentation for the `latest committed changes
+      <https://github.com/protocolbuffers/protobuf/tree/master/python>`_ of
+      the `Protocol Buffers package for Python
+      <https://developers.google.com/protocol-buffers/docs/pythontutorial>`_.
+      Some features may not yet be released. Read the documentation for the
+      latest released package at `googleapis.dev
+      <https://googleapis.dev/python/protobuf/latest/>`_.
+
 google.protobuf.empty_pb2
 =========================
 

python/docs/google/protobuf/field_mask_pb2.rst

@@ -1,5 +1,17 @@
 .. DO NOT EDIT, generated by generate_docs.py.
 
+.. ifconfig:: build_env == 'readthedocs'
+
+   .. warning::
+
+      You are reading the documentation for the `latest committed changes
+      <https://github.com/protocolbuffers/protobuf/tree/master/python>`_ of
+      the `Protocol Buffers package for Python
+      <https://developers.google.com/protocol-buffers/docs/pythontutorial>`_.
+      Some features may not yet be released. Read the documentation for the
+      latest released package at `googleapis.dev
+      <https://googleapis.dev/python/protobuf/latest/>`_.
+
 google.protobuf.field_mask_pb2
 ==============================
 

python/docs/google/protobuf/json_format.rst

@@ -1,5 +1,17 @@
 .. DO NOT EDIT, generated by generate_docs.py.
 
+.. ifconfig:: build_env == 'readthedocs'
+
+   .. warning::
+
+      You are reading the documentation for the `latest committed changes
+      <https://github.com/protocolbuffers/protobuf/tree/master/python>`_ of
+      the `Protocol Buffers package for Python
+      <https://developers.google.com/protocol-buffers/docs/pythontutorial>`_.
+      Some features may not yet be released. Read the documentation for the
+      latest released package at `googleapis.dev
+      <https://googleapis.dev/python/protobuf/latest/>`_.
+
 google.protobuf.json_format
 ===========================
 

python/docs/google/protobuf/message.rst

@@ -1,5 +1,17 @@
 .. DO NOT EDIT, generated by generate_docs.py.
 
+.. ifconfig:: build_env == 'readthedocs'
+
+   .. warning::
+
+      You are reading the documentation for the `latest committed changes
+      <https://github.com/protocolbuffers/protobuf/tree/master/python>`_ of
+      the `Protocol Buffers package for Python
+      <https://developers.google.com/protocol-buffers/docs/pythontutorial>`_.
+      Some features may not yet be released. Read the documentation for the
+      latest released package at `googleapis.dev
+      <https://googleapis.dev/python/protobuf/latest/>`_.
+
 google.protobuf.message
 =======================
 

python/docs/google/protobuf/message_factory.rst

@@ -1,5 +1,17 @@
 .. DO NOT EDIT, generated by generate_docs.py.
 
+.. ifconfig:: build_env == 'readthedocs'
+
+   .. warning::
+
+      You are reading the documentation for the `latest committed changes
+      <https://github.com/protocolbuffers/protobuf/tree/master/python>`_ of
+      the `Protocol Buffers package for Python
+      <https://developers.google.com/protocol-buffers/docs/pythontutorial>`_.
+      Some features may not yet be released. Read the documentation for the
+      latest released package at `googleapis.dev
+      <https://googleapis.dev/python/protobuf/latest/>`_.
+
 google.protobuf.message_factory
 ===============================
 

python/docs/google/protobuf/proto_builder.rst

@@ -1,5 +1,17 @@
 .. DO NOT EDIT, generated by generate_docs.py.
 
+.. ifconfig:: build_env == 'readthedocs'
+
+   .. warning::
+
+      You are reading the documentation for the `latest committed changes
+      <https://github.com/protocolbuffers/protobuf/tree/master/python>`_ of
+      the `Protocol Buffers package for Python
+      <https://developers.google.com/protocol-buffers/docs/pythontutorial>`_.
+      Some features may not yet be released. Read the documentation for the
+      latest released package at `googleapis.dev
+      <https://googleapis.dev/python/protobuf/latest/>`_.
+
 google.protobuf.proto_builder
 =============================
 

python/docs/google/protobuf/reflection.rst

@@ -1,5 +1,17 @@
 .. DO NOT EDIT, generated by generate_docs.py.
 
+.. ifconfig:: build_env == 'readthedocs'
+
+   .. warning::
+
+      You are reading the documentation for the `latest committed changes
+      <https://github.com/protocolbuffers/protobuf/tree/master/python>`_ of
+      the `Protocol Buffers package for Python
+      <https://developers.google.com/protocol-buffers/docs/pythontutorial>`_.
+      Some features may not yet be released. Read the documentation for the
+      latest released package at `googleapis.dev
+      <https://googleapis.dev/python/protobuf/latest/>`_.
+
 google.protobuf.reflection
 ==========================
 

python/docs/google/protobuf/service.rst

@@ -1,5 +1,17 @@
 .. DO NOT EDIT, generated by generate_docs.py.
 
+.. ifconfig:: build_env == 'readthedocs'
+
+   .. warning::
+
+      You are reading the documentation for the `latest committed changes
+      <https://github.com/protocolbuffers/protobuf/tree/master/python>`_ of
+      the `Protocol Buffers package for Python
+      <https://developers.google.com/protocol-buffers/docs/pythontutorial>`_.
+      Some features may not yet be released. Read the documentation for the
+      latest released package at `googleapis.dev
+      <https://googleapis.dev/python/protobuf/latest/>`_.
+
 google.protobuf.service
 =======================
 

python/docs/google/protobuf/service_reflection.rst

@@ -1,5 +1,17 @@
 .. DO NOT EDIT, generated by generate_docs.py.
 
+.. ifconfig:: build_env == 'readthedocs'
+
+   .. warning::
+
+      You are reading the documentation for the `latest committed changes
+      <https://github.com/protocolbuffers/protobuf/tree/master/python>`_ of
+      the `Protocol Buffers package for Python
+      <https://developers.google.com/protocol-buffers/docs/pythontutorial>`_.
+      Some features may not yet be released. Read the documentation for the
+      latest released package at `googleapis.dev
+      <https://googleapis.dev/python/protobuf/latest/>`_.
+
 google.protobuf.service_reflection
 ==================================
 

python/docs/google/protobuf/struct_pb2.rst

@@ -1,5 +1,17 @@
 .. DO NOT EDIT, generated by generate_docs.py.
 
+.. ifconfig:: build_env == 'readthedocs'
+
+   .. warning::
+
+      You are reading the documentation for the `latest committed changes
+      <https://github.com/protocolbuffers/protobuf/tree/master/python>`_ of
+      the `Protocol Buffers package for Python
+      <https://developers.google.com/protocol-buffers/docs/pythontutorial>`_.
+      Some features may not yet be released. Read the documentation for the
+      latest released package at `googleapis.dev
+      <https://googleapis.dev/python/protobuf/latest/>`_.
+
 google.protobuf.struct_pb2
 ==========================
 

python/docs/google/protobuf/symbol_database.rst

@@ -1,5 +1,17 @@
 .. DO NOT EDIT, generated by generate_docs.py.
 
+.. ifconfig:: build_env == 'readthedocs'
+
+   .. warning::
+
+      You are reading the documentation for the `latest committed changes
+      <https://github.com/protocolbuffers/protobuf/tree/master/python>`_ of
+      the `Protocol Buffers package for Python
+      <https://developers.google.com/protocol-buffers/docs/pythontutorial>`_.
+      Some features may not yet be released. Read the documentation for the
+      latest released package at `googleapis.dev
+      <https://googleapis.dev/python/protobuf/latest/>`_.
+
 google.protobuf.symbol_database
 ===============================
 

python/docs/google/protobuf/text_encoding.rst

@@ -1,5 +1,17 @@
 .. DO NOT EDIT, generated by generate_docs.py.
 
+.. ifconfig:: build_env == 'readthedocs'
+
+   .. warning::
+
+      You are reading the documentation for the `latest committed changes
+      <https://github.com/protocolbuffers/protobuf/tree/master/python>`_ of
+      the `Protocol Buffers package for Python
+      <https://developers.google.com/protocol-buffers/docs/pythontutorial>`_.
+      Some features may not yet be released. Read the documentation for the
+      latest released package at `googleapis.dev
+      <https://googleapis.dev/python/protobuf/latest/>`_.
+
 google.protobuf.text_encoding
 =============================
 

python/docs/google/protobuf/text_format.rst

@@ -1,5 +1,17 @@
 .. DO NOT EDIT, generated by generate_docs.py.
 
+.. ifconfig:: build_env == 'readthedocs'
+
+   .. warning::
+
+      You are reading the documentation for the `latest committed changes
+      <https://github.com/protocolbuffers/protobuf/tree/master/python>`_ of
+      the `Protocol Buffers package for Python
+      <https://developers.google.com/protocol-buffers/docs/pythontutorial>`_.
+      Some features may not yet be released. Read the documentation for the
+      latest released package at `googleapis.dev
+      <https://googleapis.dev/python/protobuf/latest/>`_.
+
 google.protobuf.text_format
 ===========================
 

python/docs/google/protobuf/timestamp_pb2.rst

@@ -1,5 +1,17 @@
 .. DO NOT EDIT, generated by generate_docs.py.
 
+.. ifconfig:: build_env == 'readthedocs'
+
+   .. warning::
+
+      You are reading the documentation for the `latest committed changes
+      <https://github.com/protocolbuffers/protobuf/tree/master/python>`_ of
+      the `Protocol Buffers package for Python
+      <https://developers.google.com/protocol-buffers/docs/pythontutorial>`_.
+      Some features may not yet be released. Read the documentation for the
+      latest released package at `googleapis.dev
+      <https://googleapis.dev/python/protobuf/latest/>`_.
+
 google.protobuf.timestamp_pb2
 =============================
 

python/docs/google/protobuf/type_pb2.rst

@@ -1,5 +1,17 @@
 .. DO NOT EDIT, generated by generate_docs.py.
 
+.. ifconfig:: build_env == 'readthedocs'
+
+   .. warning::
+
+      You are reading the documentation for the `latest committed changes
+      <https://github.com/protocolbuffers/protobuf/tree/master/python>`_ of
+      the `Protocol Buffers package for Python
+      <https://developers.google.com/protocol-buffers/docs/pythontutorial>`_.
+      Some features may not yet be released. Read the documentation for the
+      latest released package at `googleapis.dev
+      <https://googleapis.dev/python/protobuf/latest/>`_.
+
 google.protobuf.type_pb2
 ========================
 

python/docs/google/protobuf/wrappers_pb2.rst

@@ -1,5 +1,17 @@
 .. DO NOT EDIT, generated by generate_docs.py.
 
+.. ifconfig:: build_env == 'readthedocs'
+
+   .. warning::
+
+      You are reading the documentation for the `latest committed changes
+      <https://github.com/protocolbuffers/protobuf/tree/master/python>`_ of
+      the `Protocol Buffers package for Python
+      <https://developers.google.com/protocol-buffers/docs/pythontutorial>`_.
+      Some features may not yet be released. Read the documentation for the
+      latest released package at `googleapis.dev
+      <https://googleapis.dev/python/protobuf/latest/>`_.
+
 google.protobuf.wrappers_pb2
 ============================
 

python/docs/index.rst

@@ -3,6 +3,18 @@
    You can adapt this file completely to your liking, but it should at least
    contain the root `toctree` directive.
 
+.. ifconfig:: build_env == 'readthedocs'
+
+   .. warning::
+
+      You are reading the documentation for the `latest committed changes
+      <https://github.com/protocolbuffers/protobuf/tree/master/python>`_ of
+      the `Protocol Buffers package for Python
+      <https://developers.google.com/protocol-buffers/docs/pythontutorial>`_.
+      Some features may not yet be released. Read the documentation for the
+      latest released package at `googleapis.dev
+      <https://googleapis.dev/python/protobuf/latest/>`_.
+
 Protocol Buffers Python API Reference
 =====================================
 

python/setup.py

@@ -19,17 +19,23 @@ from distutils.command.build_py import build_py as _build_py
 from distutils.command.clean import clean as _clean
 from distutils.spawn import find_executable
 
+
+current_dir = os.path.dirname(__file__)
+current_dir_relative = os.path.relpath(current_dir)
+src_dir = os.path.abspath(os.path.join(current_dir, "..", "src"))
+vsprojects_dir = os.path.abspath(os.path.join(current_dir, "..", "vsprojects"))
+
 # Find the Protocol Compiler.
 if 'PROTOC' in os.environ and os.path.exists(os.environ['PROTOC']):
   protoc = os.environ['PROTOC']
-elif os.path.exists("../src/protoc"):
+elif os.path.exists(os.path.join(src_dir, "protoc")):
-  protoc = "../src/protoc"
+  protoc = os.path.join(src_dir, "protoc")
-elif os.path.exists("../src/protoc.exe"):
+elif os.path.exists(os.path.join(src_dir, "protoc.exe")):
-  protoc = "../src/protoc.exe"
+  protoc = os.path.join(src_dir, "protoc.exe")
-elif os.path.exists("../vsprojects/Debug/protoc.exe"):
+elif os.path.exists(os.path.join(vsprojects_dir, "Debug", "protoc.exe")):
-  protoc = "../vsprojects/Debug/protoc.exe"
+  protoc = os.path.join(vsprojects_dir, "Debug", "protoc.exe")
-elif os.path.exists("../vsprojects/Release/protoc.exe"):
+elif os.path.exists(os.path.join(vsprojects_dir, "Release", "protoc.exe")):
-  protoc = "../vsprojects/Release/protoc.exe"
+  protoc = os.path.join(vsprojects_dir, "Release", "protoc.exe")
 else:
   protoc = find_executable("protoc")
 
@@ -40,7 +46,7 @@ def GetVersion():
   Do not import google.protobuf.__init__ directly, because an installed
   protobuf library may be loaded instead."""
 
-  with open(os.path.join('google', 'protobuf', '__init__.py')) as version_file:
+  with open(os.path.join(current_dir, 'google', 'protobuf', '__init__.py')) as version_file:
     exec(version_file.read(), globals())
     global __version__
     return __version__
@@ -51,15 +57,21 @@ def generate_proto(source, require = True):
   .proto file.  Does nothing if the output already exists and is newer than
   the input."""
 
+  original_source = source
+  source = source.replace("../src", src_dir)
+
   if not require and not os.path.exists(source):
     return
 
-  output = source.replace(".proto", "_pb2.py").replace("../src/", "")
+  output = os.path.join(
+    current_dir,
+    original_source.replace(".proto", "_pb2.py").replace("../src/", "")
+  )
 
   if (not os.path.exists(output) or
       (os.path.exists(source) and
        os.path.getmtime(source) > os.path.getmtime(output))):
-    print("Generating %s..." % output)
+    print("Generating %s..." % os.path.relpath(output))
 
     if not os.path.exists(source):
       sys.stderr.write("Can't find required file: %s\n" % source)
@@ -71,7 +83,13 @@ def generate_proto(source, require = True):
           "or install the binary package.\n")
       sys.exit(-1)
 
-    protoc_command = [ protoc, "-I../src", "-I.", "--python_out=.", source ]
+    protoc_command = [
+      protoc,
+      "-I{}".format(src_dir),
+      "-I{}".format(current_dir),
+      "--python_out={}".format(current_dir),
+      source,
+    ]
     if subprocess.call(protoc_command) != 0:
       sys.exit(-1)
 
@@ -116,7 +134,7 @@ def GenerateUnittestProtos():
 class clean(_clean):
   def run(self):
     # Delete generated files in the code tree.
-    for (dirpath, dirnames, filenames) in os.walk("."):
+    for (dirpath, dirnames, filenames) in os.walk(current_dir):
       for filename in filenames:
         filepath = os.path.join(dirpath, filename)
         if filepath.endswith("_pb2.py") or filepath.endswith(".pyc") or \
@@ -269,7 +287,14 @@ if __name__ == '__main__':
         "Programming Language :: Python :: 3.7",
         ],
       namespace_packages=['google'],
+      # package_dir is required when setup.py is not run from the python/
+      # directory (such as from the ReadTheDocs build). See
+      # https://setuptools.readthedocs.io/en/latest/setuptools.html#using-find-packages
+      # package_dir must be a relative path. See:
+      # https://stackoverflow.com/a/53547931/101923
+      package_dir={"": current_dir_relative},
       packages=find_packages(
+          where=current_dir,
           exclude=[
               'import_test_package',
           ],