SF bug 478425: Change in os.path.join (ntpath.py)

ntpath.join('a', '') was producing 'a' instead of 'a\\' as in 2.1.
Impossible to guess what was ever *intended*, but since split('a\\')
produces ('a', ''), I think it's best if join('a', '') gives 'a\\' back.

Lib/ntpath.py

@@ -82,6 +82,12 @@ def join(a, *p):
                     path += b
                 else:
                     path += "\\" + b
+            else:
+                # path is not empty and does not end with a backslash,
+                # but b is empty; since, e.g., split('a/') produces
+                # ('a', ''), it's best if join() adds a backslash in
+                # this case.
+                path += '\\'
 
     return path