Use psycopg2cffi only if there is no psycopg2

issue11329
review354791002

trytond/backend/postgresql/database.py

@@ -12,11 +12,12 @@ from itertools import chain, repeat
 from threading import RLock
 
 try:
+    from psycopg2 import connect
+except ImportError:
     from psycopg2cffi import compat
     compat.register()
-except ImportError:
-    pass
-from psycopg2 import Binary, connect
+    from psycopg2 import connect
+from psycopg2 import Binary
 from psycopg2.extensions import (
     ISOLATION_LEVEL_AUTOCOMMIT, ISOLATION_LEVEL_REPEATABLE_READ, UNICODE, AsIs,
     cursor, register_adapter, register_type)