Conditional psycopg2cffi import for pypy3

tests/tornado_session_tests.py

@@ -5,7 +5,10 @@ Tests for functionality in the tornado_session module
 import mock
 import unittest
-from psycopg2 import extras
+try:
+    from psycopg2cffi import extras
+except ImportError:
+    from psycopg2 import extras
 from tornado import concurrent
 from tornado import gen