The make_script_temp function is rather peculiar because mkstemp() does not actually rely on the umask value (per POSIX, no matter what manpages may say).
scl-utils-20130529-1.fc18 has been submitted as an update for Fedora 18. https://admin.fedoraproject.org/updates/scl-utils-20130529-1.fc18
scl-utils-20130529-1.fc19 has been submitted as an update for Fedora 19. https://admin.fedoraproject.org/updates/scl-utils-20130529-1.fc19
Package scl-utils-20130529-1.fc19: * should fix your issue, * was pushed to the Fedora 19 testing repository, * should be available at your local mirror within two days. Update it with: # su -c 'yum update --enablerepo=updates-testing scl-utils-20130529-1.fc19' as soon as you are able to. Please go to the following url: https://admin.fedoraproject.org/updates/FEDORA-2013-11254/scl-utils-20130529-1.fc19 then log in and leave karma (feedback).
scl-utils-20130529-1.fc19 has been pushed to the Fedora 19 stable repository. If problems still persist, please make note of it in this bug report.