Update testtools/compat.py

Author: mtreinish

testtools/compat.py

@@ -18,7 +18,7 @@
 import os
 import sys
 import unicodedata
-# ensure retrocompatibility < 3.10
+# Ensure retro-compatibility with older testtools releases
 from io import StringIO, BytesIO
 
 
@@ -154,4 +154,3 @@ def _get_exception_encoding():
     #                setting that can change after the message is formatted.
     return locale.getlocale(locale.LC_MESSAGES)[1] or "ascii"
 
-