Handle log message interpolation by the logger in compute/

According to OpenStack Guideline[1], logged string message should be
interpolated by the logger.

[1]: http://docs.openstack.org/developer/oslo.i18n/guidelines.html#adding-variables-to-log-messages

Change-Id: Ib7b5fb5f794026fc8a84260c4803afea321a9cf5
Closes-Bug: #1596829

openstackclient/compute/v2/keypair.py

@@ -106,8 +106,7 @@ class DeleteKeypair(command.Command):
             except Exception as e:
                 result += 1
                 LOG.error(_("Failed to delete key with name "
-                          "'%(name)s': %(e)s")
-                          % {'name': n, 'e': e})
+                          "'%(name)s': %(e)s"), {'name': n, 'e': e})
 
         if result > 0:
             total = len(parsed_args.name)