call engine.dispose() before setting to None in close()

Author: adamhadani

rdflib_sqlalchemy/store.py

@@ -253,6 +253,7 @@ def close(self, commit_pending_transaction=False):
         Close the current store engine connection if one is open.
 
         """
+        self.engine.dispose()
         self.engine = None
 
     def destroy(self, configuration):