appveyor, #533: enable CYGWIN TCs without failing
appveyor, #533: enable CYGWIN TCs without failing

- Cygwin TCs failing (start, no Cygwin specific code):
  - PY2: err: 44, fail: 0
  - PY3: err: 13, fail: 0

gitpython-developers/gitpython,nvie/GitPython,breavo/GitPython,jeblair/GitPython,nvie/GitPython,breavo/GitPython,jeblair/GitPython,gitpython-developers/GitPython,gitpython-developers/GitPython,gitpython-developers/gitpython