Postorius crashes on saving "Message Acceptance" settings.

[Dmitry]

Hello.
I just installed maiman-bundler according to http://mailman-bundler.readthedocs.org/en/latest/ .
When I trying to save settings at Lists -> "listname" -> Settings -> Message Acceptance, I got 500 Internal Server Error with such traceback:

ERROR 2015-04-21 09:23:53,854 base 19674 -1217132864 Internal Server Error: /mailman3/lists/brian.lists.cloud-groups.com/settings/message_acceptance
Traceback (most recent call last):
  File "/home/mailman/mailman-bundler/eggs/Django-1.7.7-py2.7.egg/django/core/handlers/base.py", line 111, in get_response
    response = wrapped_callback(request, *callback_args, **callback_kwargs)
  File "/home/mailman/mailman-bundler/eggs/postorius-1.0.0-py2.7.egg/postorius/auth/decorators.py", line 58, in wrapper
    return fn(*args, **kwargs)
  File "/home/mailman/mailman-bundler/eggs/postorius-1.0.0-py2.7.egg/postorius/views/list.py", line 787, in list_settings
    except HTTPError as e:
UnboundLocalError: local variable 'HTTPError' referenced before assignment
ERROR 2015-04-21 09:23:53,854 base 19674 -1217132864 Internal Server Error: /mailman3/lists/brian.lists.cloud-groups.com/settings/message_acceptance
Traceback (most recent call last):
  File "/home/mailman/mailman-bundler/eggs/Django-1.7.7-py2.7.egg/django/core/handlers/base.py", line 111, in get_response
    response = wrapped_callback(request, *callback_args, **callback_kwargs)
  File "/home/mailman/mailman-bundler/eggs/postorius-1.0.0-py2.7.egg/postorius/auth/decorators.py", line 58, in wrapper
    return fn(*args, **kwargs)
  File "/home/mailman/mailman-bundler/eggs/postorius-1.0.0-py2.7.egg/postorius/views/list.py", line 787, in list_settings
    except HTTPError as e:
UnboundLocalError: local variable 'HTTPError' referenced before assignment
ERROR 2015-04-21 09:23:53,854 base 19674 -1217132864 Internal Server Error: /mailman3/lists/brian.lists.cloud-groups.com/settings/message_acceptance
Traceback (most recent call last):
  File "/home/mailman/mailman-bundler/eggs/Django-1.7.7-py2.7.egg/django/core/handlers/base.py", line 111, in get_response
    response = wrapped_callback(request, *callback_args, **callback_kwargs)
  File "/home/mailman/mailman-bundler/eggs/postorius-1.0.0-py2.7.egg/postorius/auth/decorators.py", line 58, in wrapper
    return fn(*args, **kwargs)
  File "/home/mailman/mailman-bundler/eggs/postorius-1.0.0-py2.7.egg/postorius/views/list.py", line 787, in list_settings
    except HTTPError as e:
UnboundLocalError: local variable 'HTTPError' referenced before assignment

After reloading page I see that settings are saved.

OS Vession: CentOS 6.5
Python versions (built from sources): 2.7.9 and 3.4.3

[Zack Piper (zack-piper123)]

Also get the same error.