Declare 'google' namespace when importing Python protobuf via Bazel.
`python/google/__init__.py` declares the top-level 'google' namespace so that
`google.protobuf` can be imported alongside other Google Python modules like
`google.auth`.
This works well when installing protobuf via Pip, but the Bazel `//:python_srcs`
rule doesn't include this file in its `srcs`. Bazel implicitly creates an empty
`google/__init__.py`, which does *not* set up a namespace. The result is that
consuming Python protobuf via Bazel breaks all other Google Python libraries.
This fixes #4658.
diff --git a/BUILD b/BUILD
index 6c62583..0cc0e29 100644
--- a/BUILD
+++ b/BUILD
@@ -640,6 +640,7 @@
name = "python_srcs",
srcs = glob(
[
+ "python/google/__init__.py",
"python/google/protobuf/*.py",
"python/google/protobuf/**/*.py",
],
