list_objecst: fix parsing user metadata as per MinIO server (#1240)

minio/datatypes.py

@@ -214,11 +214,13 @@ def fromxml(cls, element, bucket_name, is_delete_marker=False,
             else (findtext(tag, "ID"), findtext(tag, "DisplayName"))
         )
 
-        tag = find(element, "UserMetadata") or []
         metadata = {}
-        for child in tag:
-            key = child.tag.split("}")[1] if "}" in child.tag else child.tag
-            metadata[key] = child.text
+        selement = find(element, "UserMetadata")
+        if selement:
+            for child in findall(selement, "Items"):
+                key = findtext(child, "Key", True)
+                value = findtext(child, "Value", True)
+                metadata[key] = value
 
         object_name = findtext(element, "Key", True)
         if encoding_type == "url":