Correct reraising of exception

When an exception was caught and rethrown,
it should call 'raise' without any arguments
because it shows the place where an exception
occured initially instead of place where the exception re-raised.

Change-Id: I5fb6dea5da7fb6e1e2b339a713c7d37f8c99e407

openstackclient/shell.py

@@ -331,10 +331,10 @@ class OpenStackShell(app.App):
                     'auth_type': auth_type,
                 },
             )
-        except (IOError, OSError) as e:
+        except (IOError, OSError):
             self.log.critical("Could not read clouds.yaml configuration file")
             self.print_help_if_requested()
-            raise e
+            raise
 
         # TODO(thowe): Change cliff so the default value for debug
         # can be set to None.