mercurial/commands.py

--- a/mercurial/commands.py	Thu Oct 15 22:36:08 2020 -0700
+++ b/mercurial/commands.py	Thu Oct 15 22:36:17 2020 -0700
@@ -6317,9 +6317,8 @@
     Returns 0 on success.
     """
 
+    cmdutil.check_incompatible_arguments(opts, 'stdio', ['cmdserver'])
     opts = pycompat.byteskwargs(opts)
-    if opts[b"stdio"] and opts[b"cmdserver"]:
-        raise error.Abort(_(b"cannot use --stdio with --cmdserver"))
     if opts[b"print_url"] and ui.verbose:
         raise error.Abort(_(b"cannot use --print-url with --verbose"))