Normalized paths in test_commons.py to make tests platform-independent

[kremnik]

Tickets

#1337

What has been done

With this PR, paths processing in test_commons.py was added. Due to direct path comparisons in test_commons.py without considering the OS, the tests were failing on Windows (an example is shown below). This change adds path normalization using os.path.normpath to make the paths platform-independent.

Example of the error in Windows 10:

AssertionError: expected call not found.
Expected: download('http://example.com/model_weights.bz2', '/mock/home/.deepface/weights/model_weights.h5.bz2', quiet=False)
Actual: download('http://example.com/model_weights.bz2', '/mock/home\\.deepface/weights\\model_weights.h5.bz2', quiet=False)

How to test

cd tests && python -m pytest test_commons.py -s --disable-warnings

[serengil]

LGTM