[1.11.x] Fixed #28488 -- Reallowed error handlers to access CSRF tokens.

Regression in eef95ea96f.

Backport of c4c128d67c from master

tests/csrf_tests/views.py

@@ -1,7 +1,8 @@
 from __future__ import unicode_literals
 
 from django.http import HttpResponse
-from django.template import RequestContext, Template
+from django.middleware.csrf import get_token
+from django.template import Context, RequestContext, Template
 from django.template.context_processors import csrf
 from django.views.decorators.csrf import ensure_csrf_cookie
 
@@ -30,3 +31,9 @@ def non_token_view_using_request_processor(request):
     context = RequestContext(request, processors=[csrf])
     template = Template('')
     return HttpResponse(template.render(context))
+
+
+def csrf_token_error_handler(request, **kwargs):
+    """This error handler accesses the CSRF token."""
+    template = Template(get_token(request))
+    return HttpResponse(template.render(Context()), status=599)