diff -r fba2d7fab11e -r 937998e43e93 mercurial/merge.py
--- a/mercurial/merge.py	Thu Feb 03 06:49:48 2022 +0100
+++ b/mercurial/merge.py	Fri Jan 28 14:23:37 2022 +0100
@@ -41,10 +41,9 @@
     valid = [b'abort', b'ignore', b'warn']
     if config not in valid:
         validstr = b', '.join([b"'" + v + b"'" for v in valid])
-        raise error.ConfigError(
-            _(b"%s.%s not valid ('%s' is none of %s)")
-            % (section, name, config, validstr)
-        )
+        msg = _(b"%s.%s not valid ('%s' is none of %s)")
+        msg %= (section, name, config, validstr)
+        raise error.ConfigError(msg)
     return config