words: fix alphabet_sort exception handling for py3.14

As of python/cpython#121395, the format of the
list.index exception has changed and parsing it like this no longer
works. Relying on implementation details like this is always risky, so
this solution should be more future-proof.

Author: gotmax23

domdf_python_tools/words.py

@@ -171,14 +171,13 @@ def alpha_sort(
 
 	alphabet_ = list(alphabet)
 
-	try:
-		return sorted(iterable, key=lambda attr: [alphabet_.index(letter) for letter in attr], reverse=reverse)
-	except ValueError as e:
-		m = re.match(r"'(.*)' is not in list", str(e))
-		if m:
-			raise ValueError(f"The character {m.group(1)!r} was not found in the alphabet.") from None
-		else:  # pragma: no cover
-			raise e
+	def _alphabet_index(letter: str) -> int:
+		try:
+			return alphabet_.index(letter)
+		except ValueError:
+			raise ValueError(f"The character {letter!r} was not found in the alphabet.") from None
+
+	return sorted(iterable, key=lambda attr: [_alphabet_index(letter) for letter in attr], reverse=reverse)
 
 
 class Font(Dict[str, str]):