Fixed error and some warning returned by pylint

apps/filesystem_serving/views.py

@@ -1,5 +1,5 @@
 from django.utils.translation import ugettext_lazy as _
-from django.http import HttpResponse, HttpResponseRedirect, Http404
+from django.http import HttpResponseRedirect
 from django.shortcuts import render_to_response
 from django.template import RequestContext
 from django.contrib import messages