pytest.skip() must not be used at module level because it can easily be
misunderstood and used as a decorator instead of pytest.mark.skip, causing the
whole module to be skipped instead of just the test being decorated.
This is unexpected for users used to the @unittest.skip decorator and therefore
it is best to bail out with a clean error when it happens.
The pytest equivalent of @unittest.skip is @pytest.mark.skip .
Adapt existing tests that were actually relying on this behaviour and add a
test that explicitly test that collection fails.
fix#607
d81f23009b