fix(sqlalchemy): check if sesison has autoflush attribute

Tests were braking, this will fix it.

Refs: #449

firenado/sqlalchemy.py

@@ -133,7 +133,7 @@ def wrapper(self, *method_args, **method_kwargs):
                 if not session:
                     logger.warning("No session was resolved.")
                 logger.debug("Closing session %s.", session)
-                if not session.autoflush:
+                if hasattr(session, "autoflush") and not session.autoflush:
                     session.flush()
                 session.close()
             return result