remove import dummp_os

Lib/genericpath.py

@@ -3,10 +3,7 @@ Path operations common to more than one OS
 Do not use directly.  The OS specific modules import the appropriate
 functions from this module themselves.
 """
-try:
-    import os
-except ImportError:
-    import _dummy_os as os
+import os
 import stat
 
 __all__ = ['commonprefix', 'exists', 'getatime', 'getctime', 'getmtime',