I just released mock 1.2.16. From the release notes:
https://fedoraproject.org/wiki/1.2.16
mock-1.2.16 has been released to get rid of annoying errors due selinux
RHBZ#1312820
Additionally mock-1.2.16 introduces these changes:
* sparc configs has been removed
* instead of systemd-nspawn mock now requires systemd-container in F24+
And several bugfixes:
* do not call /bin/su and rather utilize --user of systemd-nspawn
RHBZ#1301953
* tell nspawn which variables it should set RHBZ#1311796
Known issue:
* When you run mockchain with several SRPMs, then it may fails due
deluser bug RHBZ#1315864