pythongh-135069: Fix exception message in encodings.idna module (python#135071)

Author: danielhollas

Lib/encodings/idna.py

@@ -316,7 +316,7 @@ def _buffer_encode(self, input, errors, final):
 class IncrementalDecoder(codecs.BufferedIncrementalDecoder):
     def _buffer_decode(self, input, errors, final):
         if errors != 'strict':
-            raise UnicodeError("Unsupported error handling: {errors}")
+            raise UnicodeError(f"Unsupported error handling: {errors}")
 
         if not input:
             return ("", 0)

Misc/NEWS.d/next/Library/2025-06-03-12-59-17.gh-issue-135069.xop30V.rst

@@ -0,0 +1,3 @@
+Fix the "Invalid error handling" exception in
+:class:`!encodings.idna.IncrementalDecoder` to correctly replace the
+'errors' parameter.