py_library import path is wrong for certain pypi packages (like tensorflow)

[WesleyYue]

Inside where the py_library() is generated for each specified requirement, the import path is specified as "." (https://github.com/bazelbuild/rules_python/blob/master/rules_python/whl.py#L149). While this works for most packages, not all packages have the python module in the top level of the whl. For example, the tensorflow python module is inside tensorfow-<version_info>.whl/tensorfow-<version_info>.data/purelib/tensorflow. Because of this, import tensorflow will fail in a py_binary that has requirement("tensorflow"). What I believe rules_python/whl.py should be doing is to check whether the top-level folders have an __init__.py file inside of them, and if not, search the directory tree until it finds them.

[danieljanes]

Thanks for opening this issue @WesleyYue. This is a huge blocker for us as well and I believe there is related info in #71 (and apt-itude/rules_pip#15).

[alexeagle]

rules_python 0.1.0 has been released which upstreams the rules_python_external repo. Please switch from pip_import to pip_install which doesn't have this issue.