clean up test_trace_callback_content explicitly

Author: Erlend E. Aasland

Lib/sqlite3/test/hooks.py

@@ -261,6 +261,11 @@ def trace(statement):
         cur.execute(queries[1])
         self.assertEqual(traced_statements, queries)
 
+        con1.close()
+        con2.close()
+        import gc
+        gc.collect()
+
 
 def suite():
     tests = [