User.DoesNotExist: User matching query does not exist.

[sentry]

Sentry Issue: ACS-INTERFACE-Y

User.DoesNotExist: User matching query does not exist.
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  File "django/core/handlers/base.py", line 179, in _get_response
    response = wrapped_callback(request, *callback_args, **callback_kwargs)
  File "django/contrib/auth/decorators.py", line 21, in _wrapped_view
    return view_func(request, *args, **kwargs)
  File "/opt/interface/interface/views.py", line 312, in subs_for_user
    user = User.objects.get(username=username)
  File "django/db/models/manager.py", line 85, in manager_method
    return getattr(self.get_queryset(), name)(*args, **kwargs)
  File "django/db/models/query.py", line 431, in get
    self.model._meta.object_name