Fix uncollect when no data pass through to it (pytest 2.7.0 bug)

[jkrocil]

Fix uncollect when no data pass through to it (pytest 2.7.0 bug, issue #510)
Parametrize using testgen to utilize param check everywhere
Rename skip funcs to uncollect so their names match their purpose

[jkrocil]

This might fix some issues but introduce new failures; it could uncover new problems.

[RonnyPfannschmidt]

for references pytest-dev/pytest#510 and the fix merged by pytest-dev/pytest#1530

pytest release pending, it should be easier to fix after merging #2661

[jkrocil]

@RonnyPfannschmidt this PR will ensure that when we pass argnames but no argvalues to parametrize, it will not err but it will also not create a skipping test. It will uncollect it completely. This is done a) through testgen.parametrize which utilizes testgen.param_check which checks arvalues for data and marks the test with mark.uncollect if no data were found or b) even if test is not passed through testgen.parametrize but just metafunc.parametrize without the param_check, we do the check for argvalues inside the pytest_collection_modifyitems hook.

So once the PR is merged and we run pytest 2.9.0, we will still want to have this change in place if I understand correctly because pytest will never completely uncollect a test, there will always be at least a single skipping item. Right?

[RonnyPfannschmidt]

correct, we might want to ensure thats documented then

[dajoRH]

Lint report for commit f8423ce:

Everything seems all right 😄 .
CFME QE Bot