Fixes #105

lemur/common/managers.py

@@ -22,6 +22,7 @@ class InstanceManager(object):
 
     def add(self, class_path):
         self.cache = None
+        if class_path not in self.class_list:
             self.class_list.append(class_path)
 
     def remove(self, class_path):

lemur/plugins/views.py

@@ -86,7 +86,7 @@ class PluginsList(AuthenticatedResource):
         if args['type']:
             return list(plugins.all(plugin_type=args['type']))
 
-        return plugins.all()
+        return list(plugins.all())
 
 
 class Plugins(AuthenticatedResource):