PYTHON-2136: added more diagnostic information for ServerSelectionTimeoutError (#444)

* PYTHON-2136: added more diagnostic information for ServerSelectionTimeoutError

* made error message more human readable

* fixed tests

* fixed remaining testcase

* fixed formatting

* more formatting fixes

Author: juliusgeo

pymongo/topology.py

@@ -213,7 +213,8 @@ def _select_servers_loop(self, selector, timeout, address):
             # No suitable servers.
             if timeout == 0 or now > end_time:
                 raise ServerSelectionTimeoutError(
-                    self._error_message(selector))
+                    "%s, Timeout: %ss, Topology Description: %r" %
+                    (self._error_message(selector), timeout, self.description))
 
             self._ensure_opened()
             self._request_check_all()

test/test_replica_set_client.py

@@ -343,8 +343,7 @@ def test_connect_with_internal_ips(self):
         with self.assertRaises(AutoReconnect) as context:
             connected(client)
 
-        self.assertEqual(
-            "Could not reach any servers in [('internal-ip', 27017)]."
+        self.assertIn("Could not reach any servers in [('internal-ip', 27017)]."
             " Replica set is configured with internal hostnames or IPs?",
             str(context.exception))
 

test/test_topology.py

@@ -766,7 +766,7 @@ def assertMessage(self, message, topology, selector=any_server_selector):
         with self.assertRaises(ConnectionFailure) as context:
             topology.select_server(selector, server_selection_timeout=0)
 
-        self.assertEqual(message, str(context.exception))
+        self.assertIn(message, str(context.exception))
 
     def test_no_primary(self):
         t = create_mock_topology(replica_set_name='rs')