Use 'except ... as' syntax

This syntax works on Python 2.6 through 3.x.  lib/ansible/module_utils
(and lib/ansible/modules) need to support Python 2.4, so I didn't touch
those.

lib/ansible/utils/path.py

@@ -45,6 +45,6 @@ def makedirs_safe(path, mode=None):
                 os.makedirs(path, mode)
             else:
                 os.makedirs(path)
-        except OSError, e:
+        except OSError as e:
             if e.errno != EEXIST:
                 raise