Remove source=self from ResourceWarning

Removing source=self prevents unraisable exception in C extension.
The warning message still contains the filename via %r formatting.

Signed-off-by: Osama Abdelkader <[email protected]>

Author: osamakader

Lib/xml/etree/ElementTree.py

@@ -1271,8 +1271,7 @@ def close(self):
 
         def __del__(self, _warn=warnings.warn):
             if close_source:
-                _warn("unclosed file %r" % (source,),
-                      ResourceWarning, source=self)
+                _warn("unclosed file %r" % (source,), ResourceWarning)
                 source.close()
 
     it = IterParseIterator()