Use pkgutil to allow successfully work with python packages that contain google or google/protobuf

[tbetbetbe]

google/protobuf is a key dependency of python grpc.

Shortly, gRPC-based will be published that contain either a top-level 'google' package, and in some cases other modules in the google/protobuf package.

At the moment using, any of these other packages will generally fail because the protobuf package is installed

• the other google package will contain modules with the google package (sometimes in google/protobuf)
• when the protobuf package is installed, both google and google/protobuf end up being resolved to the protobuf package
• other paths on the sys.path are not searched

The result is importing modules from the other packages ends with 'No module named logging.v1' for snippets like:

from google.logging.v1 import ....

There is well-known way to resolve this using pkgutil

• Use pkgutil.extend_path inside the init.py of the google and google/protobuf packages
  E.g,

import pkgutil
__path__ = pkgutil.extend_path(__path__, __name__)

A good online resource explaining this use of pkgutil is available at pymotw:pkgutil

[haberman]

Is this the same problem as described in #713 ?

This is one of those issues that I'd be happy to accept a PR for. The only reason I haven't fixed it already is because the Python packaging ecosystem is (to me) really complicated and subtle, and so it often takes a lot of background research for me to determine exactly what the right fix is.

[xfxyjwf]

Same issue here: #1153

[haberman]

Closing in favor of #1296