better error message in checkSession in tests

rhodecode/tests/__init__.py

@@ -157,4 +157,8 b' class TestController(TestCase):'
 
     def checkSessionFlash(self, response, msg):
         self.assertTrue('flash' in response.session)
-        self.assertTrue(msg in response.session['flash'][0][1])
+        if not msg in response.session['flash'][0][1]:
+            self.fail(
+                'msg `%s` not found in session flash: got `%s` instead' % (
+                      msg, response.session['flash'][0][1])
+            )