test_svnwc.py is failing on Windows

[nicoddemus]

Output of the failures from AppVeyor in build 1.0.8: https://gist.github.com/nicoddemus/85b100282dabab1d1b7acd98c8795059

Skipping those tests for now until someone interested wants to pick this up.

[RonnyPfannschmidt]

shouldnt we use xfail(run=False) ?

[nicoddemus]

Of course, thanks for the pointer. Updated the PR.