[1.5.x] Fixed #20237 -- Reenabled assertContains with binary parameter

Thanks Baptiste Mispelon for the review.
Backport of fe01404bb9 from master.

tests/regressiontests/test_client_regress/tests.py

@@ -131,6 +131,13 @@ class AssertContainsTests(TestCase):
         self.assertNotContains(r, 'はたけ')
         self.assertNotContains(r, b'\xe3\x81\xaf\xe3\x81\x9f\xe3\x81\x91'.decode('utf-8'))
 
+    def test_binary_contains(self):
+        r = self.client.get('/test_client_regress/check_binary/')
+        self.assertContains(r, b'PDF document')
+        with self.assertRaises(AssertionError):
+            self.assertContains(r, b'PDF document', count=2)
+        self.assertNotContains(r, b'ODF document')
+
     def test_nontext_contains(self):
         r = self.client.get('/test_client_regress/no_template_view/')
         self.assertContains(r, ugettext_lazy('once'))

tests/regressiontests/test_client_regress/urls.py

@@ -28,6 +28,7 @@ urlpatterns = patterns('',
     (r'^check_session/$', views.check_session_view),
     (r'^request_methods/$', views.request_methods_view),
     (r'^check_unicode/$', views.return_unicode),
+    (r'^check_binary/$', views.return_undecodable_binary),
     (r'^parse_unicode_json/$', views.return_json_file),
     (r'^check_headers/$', views.check_headers),
     (r'^check_headers_redirect/$', RedirectView.as_view(url='/test_client_regress/check_headers/')),

tests/regressiontests/test_client_regress/views.py

@@ -70,6 +70,11 @@ def request_methods_view(request):
 def return_unicode(request):
     return render_to_response('unicode.html')
 
+def return_undecodable_binary(request):
+    return HttpResponse(
+        b'%PDF-1.4\r\n%\x93\x8c\x8b\x9e ReportLab Generated PDF document http://www.reportlab.com'
+    )
+
 def return_json_file(request):
     "A view that parses and returns a JSON string as a file."
     match = CONTENT_TYPE_RE.match(request.META['CONTENT_TYPE'])