Added genericpath to SKIPNAMES

- this seems to fix the problem that using real os.path functions
implemented in this module are stubbed out

Author: mrbean-bremen

pyfakefs/fake_filesystem_unittest.py

@@ -226,7 +226,7 @@ class Patcher(object):
 
     # To add py.test support per issue https://github.com/jmcgeheeiv/pyfakefs/issues/43,
     # it appears that adding  'py', 'pytest', '_pytest' to SKIPNAMES will help
-    SKIPNAMES = set(['os', 'path', 'tempfile', 'io'])
+    SKIPNAMES = set(['os', 'path', 'tempfile', 'io', 'genericpath'])
     if HAS_PATHLIB:
         SKIPNAMES.add('pathlib')