[plotters][views] Add missing Http404 import

beat/web/plotters/views.py

@@ -29,7 +29,6 @@ import os
 import itertools
 import base64
 import collections
-import six
 
 import logging
 logger = logging.getLogger(__name__)
@@ -37,6 +36,7 @@ logger = logging.getLogger(__name__)
 import simplejson
 
 from django.http import HttpResponse, HttpResponseForbidden, HttpResponseBadRequest
+from django.http import Http404
 from django.conf import settings
 from django.shortcuts import render
 from django.shortcuts import get_object_or_404
@@ -44,6 +44,7 @@ from django.template import Context
 from django.contrib.auth.decorators import login_required
 from django.contrib.auth.models import User
 from django.views.generic import TemplateView
+from django.utils import six
 
 from ..experiments.models import Experiment, Block, Result
 from ..dataformats.models import DataFormat