Update to 2.6.1:

2.6.1
-----------------------------------

- No longer show line numbers in the --verbose output, the output is now
  purely the nodeid.  The line number is still shown in failure reports.
  Thanks Floris Bruynooghe.

- fix issue437 where assertion rewriting could cause pytest-xdist slaves
  to collect different tests. Thanks Bruno Oliveira.

- fix issue555: add "errors" attribute to capture-streams to satisfy
  some distutils and possibly other code accessing sys.stdout.errors.

- fix issue547 capsys/capfd also work when output capturing ("-s") is disabled.

- address issue170: allow pytest.mark.xfail(...) to specify expected exceptions via
  an optional "raises=EXC" argument where EXC can be a single exception
  or a tuple of exception classes.  Thanks David Mohr for the complete
  PR.

- fix integration of pytest with unittest.mock.patch decorator when
  it uses the "new" argument.  Thanks Nicolas Delaby for test and PR.

- fix issue with detecting conftest files if the arguments contain
  "::" node id specifications (copy pasted from "-v" output)

- fix issue544 by only removing "@NUM" at the end of "::" separated parts
  and if the part has an ".py" extension

- don't use py.std import helper, rather import things directly.
  Thanks Bruno Oliveira.

(wiz)