Fix missing to_dict and import in robots model

Also adds a test to catch this issue

endpoints/api/robot_models_interface.py

@@ -25,6 +25,11 @@ class Team(namedtuple('Team', ['name', 'avatar'])):
   :type name: string
   :type avatar: {string -> string}
   """
+  def to_dict(self):
+    return {
+      'name': self.name,
+      'avatar': self.avatar,
+    }
 
 
 class RobotWithPermissions(