--- a/mercurial/hgweb/wsgiheaders.py	Mon Jan 06 14:07:43 2025 -0500
+++ b/mercurial/hgweb/wsgiheaders.py	Mon Jan 06 14:15:40 2025 -0500
@@ -48,8 +48,8 @@
         if type(value) is bytes:
             return value
         raise AssertionError(
-            u"Header names/values must be"
-            u" of type bytes (got %s)" % repr(value)
+            "Header names/values must be"
+            " of type bytes (got %s)" % repr(value)
         )
 
     def __len__(self):