Fix: add missing self._localName assignment in xml.dom.minidom.Attr

X-Ref: python/typeshed#8590 (comment)

This adds a missing assignment to `_localName`

Author: kkirsche

Lib/xml/dom/minidom.py

@@ -358,6 +358,8 @@ def __init__(self, qName, namespaceURI=EMPTY_NAMESPACE, localName=None,
         self._name = qName
         self.namespaceURI = namespaceURI
         self._prefix = prefix
+        if localName is not None:
+            self._localName = localName
         self.childNodes = NodeList()
 
         # Add the single child node that represents the value of the attr