_deprecated_config_handler(): Use warn stacklevel for better feedback (#3884)

Author: abravalheri

changelog.d/change.rst

@@ -0,0 +1,2 @@
+Add a `stacklevel` parameter to `warnings.warn()` to provide more information to the user.
+-- by :user:`cclauss`

setuptools/config/setupcfg.py

@@ -513,7 +513,7 @@ def _deprecated_config_handler(self, func, msg, warning_class):
 
         @wraps(func)
         def config_handler(*args, **kwargs):
-            warnings.warn(msg, warning_class)
+            warnings.warn(msg, warning_class, stacklevel=2)
             return func(*args, **kwargs)
 
         return config_handler