maintainers/fix-maintainers.pl: error on unset GH_TOKEN

my $ua = LWP::UserAgent->new();

if (!defined $ENV{GH_TOKEN}) {

    die "Set GH_TOKEN before running this script";

}

keys %$maintainers_json; # reset the internal iterator so a prior each() doesn't affect the loop

while(my($k, $v) = each %$maintainers_json) {

    my $current_user = %$v{'github'};