issue 1496 - xfail with condition keyword

[tomviner]

Fix for #1496 Xfail does not work with condition keyword argument.

We were only looking at args, despite the docs saying:

Here’s the signature of the xfail marker, using Python 3 keyword-only arguments syntax:
def xfail(condition=None, *, reason=None, raises=None, run=True, strict=False):

[nicoddemus]

Cool, many thanks! 😎

[nicoddemus]

@RonnyPfannschmidt could you please take a look and merge if you are also OK with it?

[RonnyPfannschmidt]

at first glance its ok will take a deeper look in a bit

[tomviner]

@RonnyPfannschmidt I just simplified a little. I've rebased this branch, but I've pushed the edit here: tomviner@4b5640a

[nicoddemus]

@RonnyPfannschmidt did you get a chance to take a better look on this? 😁