Fix assertion rewrite to match module names correctly

[nicoddemus]

Fix #2939

@hroncok, I managed use your reproducer to verify that the fix works:

{env36} X:\setuptools [master]>python -m pytest -k test_unicode_filename_in_sdist -v --tb=line
============================= test session starts =============================
platform win32 -- Python 3.6.0, pytest-3.2.5, py-1.5.2, pluggy-0.4.0 -- X:\setuptools\.env36\Scripts\python.exe
cachedir: .cache
rootdir: X:\setuptools, inifile: pytest.ini
plugins: virtualenv-1.2.11, shutil-1.2.11, flake8-0.9.1
collected 391 items

setuptools/tests/test_easy_install.py::TestEasyInstallTest::test_unicode_filename_in_sdist FAILED

================================== FAILURES ===================================
<frozen importlib._bootstrap>:960: RecursionError: maximum recursion depth exceeded
============================ 390 tests deselected =============================
================== 1 failed, 390 deselected in 2.01 seconds ===================

Using the code from this branch fixes the issue:

{env36} X:\setuptools [master]>pip install -e c:\pytest
Obtaining file:///C:/pytest
Requirement already satisfied: py>=1.4.33 in x:\setuptools\.env36\lib\site-packages (from pytest==3.2.6.dev5+gd13086a)
Requirement already satisfied: setuptools in x:\setuptools\.env36\lib\site-packages (from pytest==3.2.6.dev5+gd13086a)
Requirement already satisfied: colorama in x:\setuptools\.env36\lib\site-packages (from pytest==3.2.6.dev5+gd13086a)
Installing collected packages: pytest
  Found existing installation: pytest 3.2.5
    Uninstalling pytest-3.2.5:
      Successfully uninstalled pytest-3.2.5
  Running setup.py develop for pytest
Successfully installed pytest

{env36} X:\setuptools [master]>python -m pytest -k test_unicode_filename_in_sdist -v --tb=line
============================= test session starts =============================
platform win32 -- Python 3.6.0, pytest-3.2.6.dev5+gd13086a, py-1.5.2, pluggy-0.4.0 -- X:\setuptools\.env36\Scripts\python.exe
cachedir: .cache
rootdir: X:\setuptools, inifile: pytest.ini
plugins: virtualenv-1.2.11, shutil-1.2.11, flake8-0.9.1
collected 391 items

setuptools/tests/test_easy_install.py::TestEasyInstallTest::test_unicode_filename_in_sdist PASSED

============================ 390 tests deselected =============================
================== 1 passed, 390 deselected in 7.82 seconds ===================

Thanks again for taking the time to analyze the issue!

[hroncok]

I'd love this to be hamster 🐹

[nicoddemus]

Heh done!

[hroncok]

Thanks.

[coveralls]

Coverage remained the same at 92.258% when pulling d13086a on nicoddemus:rewrite-bug-2939 into 77bd0aa on pytest-dev:master.

[coveralls]

Coverage remained the same at 92.258% when pulling c8d52b6 on nicoddemus:rewrite-bug-2939 into 77bd0aa on pytest-dev:master.

[The-Compiler]

LGTM - thanks! 🐹