Fixed replicaset_connection test

tests/replicaset_connection.py

@@ -1,6 +1,6 @@
 import unittest
 import pymongo
-from pymongo import ReadPreference
+from pymongo import ReadPreference, ReplicaSetConnection
 
 import mongoengine
 from mongoengine import *
@@ -17,11 +17,15 @@ class ConnectionTest(unittest.TestCase):
     def test_replicaset_uri_passes_read_preference(self):
         """Requires a replica set called "rs" on port 27017
         """
+
         try:
             conn = connect(db='mongoenginetest', host="mongodb://localhost/mongoenginetest?replicaSet=rs", read_preference=ReadPreference.SECONDARY_ONLY)
         except ConnectionError, e:
             return
 
+        if not isinstance(conn, ReplicaSetConnection):
+            return
+
         self.assertEquals(conn.read_preference, ReadPreference.SECONDARY_ONLY)
 
 if __name__ == '__main__':