Add a new warning gategory, ResourceWarning, as discussed on python-dev. It is silent by default,

except when configured --with-pydebug.

Emit this warning from the GC shutdown procedure, rather than just printing to stderr.

Lib/warnings.py

@@ -383,4 +383,11 @@ if not _warnings_defaults:
     else:
         bytes_action = "ignore"
     simplefilter(bytes_action, category=BytesWarning, append=1)
+    # resource usage warnings are enabled by default in pydebug mode
+    if hasattr(sys, 'gettotalrefcount'):
+        resource_action = "always"
+    else:
+        resource_action = "ignore"
+    simplefilter(resource_action, category=ResourceWarning, append=1)
+
 del _warnings_defaults