Add deprecated_option_warning() method to Command

This method factors out a common pattern for handling deprecated
command options.

Change-Id: I8ca8ec76365833cc8a71388e478680f7f8444be0

osc_lib/command/command.py

@@ -47,6 +47,13 @@ class Command(command.Command):
                     'to enable this command.')
             raise exceptions.CommandError(msg)
 
+    def deprecated_option_warning(self, old_option, new_option):
+        """Emit a warning for use of a deprecated option"""
+        self.log.warning(
+            _("The %(old)s option is deprecated, please use %(new)s instead.")
+            % {'old': old_option, 'new': new_option}
+        )
+
 
 class Lister(Command, lister.Lister):
     pass