astroid cannot import modules from wheels

[leifwalsh]

Steps to reproduce

1. Have a .whl file on the path, and code that imports it
2. Run pylint on the importing code

Current behavior

pylint reports an error that it cannot import the module

Expected behavior

pylint doesn't report an error

python -c "from astroid import __pkginfo__; print(__pkginfo__.version)" output

astroid 1.6.3, pylint 1.8.1

I believe the fix would be to add '.whl' to this list: https://github.com/PyCQA/astroid/blob/e0a298df55b15abcb77c2a93253f5ab7be52d0fb/astroid/manager.py#L188

I've patched astroid locally and this does allow astroid to import the module. I'm surprised we haven't seen this before, I think an older version of pylint also failed to astroid-import the module, but just didn't complain about it?

[PCManticore]

Hey @leifwalsh Thanks for creating the issue! Yes that fix might actually solve this problem and sounds reasonable. Would you mind sending a PR with that?