keep old --use-mutatormath option to print error when passed nudging …

…to ufoProcessor

Lib/fontmake/__main__.py

@@ -15,7 +15,7 @@
 import logging
 import os
 import sys
-from argparse import ArgumentParser, FileType
+from argparse import SUPPRESS, ArgumentParser, FileType
 from collections import namedtuple
 from contextlib import contextmanager
 from textwrap import dedent
@@ -308,6 +308,8 @@ def main(args=None):
  """
  ),
  )
+ # no longer show option in --help but keep to produce nice error message
+ outputGroup.add_argument("--use-mutatormath", action="store_true", help=SUPPRESS)
  outputGroup.add_argument(
  "-M",
  "--masters-as-instances",
@@ -612,6 +614,13 @@ def main(args=None):
 
  args = vars(parser.parse_args(args))
 
+ use_mutatormath = args.pop("use_mutatormath")
+ if use_mutatormath:
+ parser.error(
+ "MutatorMath is no longer supported by fontmake. "
+ "Try to use ufoProcessor: https://github.com/LettError/ufoProcessor"
+ )
+
  level = args.pop("verbose")
  _configure_logging(level, timing=args.pop("timing"))