rhg: Remove error message on unsupported CLI arguments
Like in other "unsupported" cases that return a specific exit code
Differential Revision: https://phab.mercurial-scm.org/D10002
#require test-repo jshint hg10
$ . "$TESTDIR/helpers-testrepo.sh"
run jshint on all tracked files ending in .js except vendored dependencies
$ cd "`dirname "$TESTDIR"`"
$ testrepohg locate 'set:**.js' \
> 2>/dev/null \
> | xargs jshint