python: consider emojis with expandable width

Problem: The expandable width prefix ("+:") assumes all output
characters are 1 character width in size.  This may not always be
the case, such as with several of the emoji output options.

Use wcswidth() instead of len() for calculating output width.

Author: chu11

src/bindings/python/flux/util.py

@@ -30,6 +30,7 @@
 from pathlib import Path, PurePosixPath
 from string import Formatter
 from typing import Mapping
+from wcwidth import wcswidth
 
 import yaml
 
@@ -1037,7 +1038,7 @@ def sentinel_keys():
         for item in items:
             for entry in lst:
                 result = formatter.format(entry["fmt"], item)
-                width = 0 if result in empty else len(result)
+                width = 0 if result in empty else wcswidth(result)
                 if width > entry["maxwidth"]:
                     entry["maxwidth"] = width
                 if width > entry["width"]: