Fixed #20019 -- Ensured HttpRequest.resolver_match always exists.

Obviously it isn't set until the URL is resolved.

django/http/request.py

@@ -44,6 +44,7 @@ class HttpRequest(object):
         self.path = ''
         self.path_info = ''
         self.method = None
+        self.resolver_match = None
         self._post_parse_error = False
 
     def __repr__(self):

tests/urlpatterns_reverse/tests.py

@@ -9,7 +9,7 @@ from django.core.exceptions import ImproperlyConfigured, ViewDoesNotExist
 from django.core.urlresolvers import (reverse, resolve, get_callable,
     get_resolver, NoReverseMatch, Resolver404, ResolverMatch, RegexURLResolver,
     RegexURLPattern)
-from django.http import HttpResponseRedirect, HttpResponsePermanentRedirect
+from django.http import HttpRequest, HttpResponseRedirect, HttpResponsePermanentRedirect
 from django.shortcuts import redirect
 from django.test import TestCase
 from django.utils import unittest, six
@@ -529,6 +529,10 @@ class ResolverMatchTests(TestCase):
         resolver_match = response.resolver_match
         self.assertEqual(resolver_match.url_name, 'test-resolver-match')
 
+    def test_resolver_match_on_request_before_resolution(self):
+        request = HttpRequest()
+        self.assertIsNone(request.resolver_match)
+
 class ErroneousViewTests(TestCase):
     urls = 'urlpatterns_reverse.erroneous_urls'