getfuncargvalue deprecation warning does set the proper stacklevel

[pelme]

Calling request.getfuncargvalue() gives this rather unhelpful message which makes it hard to figure out where the call happens:

...

=== warnings summary ===
system/test_asdf.py::test_fghj
  /bla/bla/bla/_pytest/fixtures.py:431: DeprecationWarning: use of getfuncargvalue is deprecated, use getfixturevalue
    DeprecationWarning)

[RonnyPfannschmidt]

@pelme i wonder if we have other warnings with that mistake as well

[pelme]

I did not look into it at this point. I have just been annoyed by this single instance for a while but not gotten around to fixing it.

Btw, I think stacklevel=2 would be a saner default in Python but anyways...