Better message in case of not using parametrized variable

[pwilczynskiclearcode]

py.test 2.9.1

In case of not using one of parametrized variables the following message is displayed:

/python2.7/site-packages/_pytest/python.py:237: in pytest_generate_tests
    metafunc.parametrize(*marker.args, **marker.kwargs)
/python2.7/site-packages/_pytest/python.py:1000: in parametrize
    raise ValueError("%r uses no fixture %r" %(self.function, arg))
E   ValueError: <function test_abc at 0x7f9bb394dde8> uses no fixture u'suffix'

where suffix isn't a fixture but missed variable from pytest.mark.parametrize.

Suggested enhancement: Raise Exception with a message suggesting using the suffix variable and not confuse developers about suffix fixture.

[The-Compiler]

It is a fixture from pytest's point of view - but I'd also be okay with the error saying "argument" instead of "fixture". "variable" is even more confusing, IMHO.

[RonnyPfannschmidt]

for parametrize, in case of direct "arguments" we should use names that make the most sense

for a good error we should take a look if there is a indirect fixture that takes parameters (needs indirect=True) or if the parameter is just missing (maybe typo detection)

[hackebrot]

I'd say we change the ValueError to report an issue

• with argument if parameter is not indirect
• with fixture if parameter is indirect

[hackebrot]

Please review #1757

[nicoddemus]

Fixed in #1757