Throw exception if mq plugin registration is not list

mq/lib/plugins.py

@@ -69,6 +69,8 @@ def registerPlugins():
                 if 'message' in dir(module):
                     mclass = module.message()
                     mreg = mclass.registration
+                    if type(mreg) != list:
+                        raise ImportError('Plugin {0} registration needs to be a list'.format(mname))
                     if 'priority' in dir(mclass):
                         mpriority = mclass.priority
                     else: