IIRC we hit this issue before when trying to install a mock rpm of a specific version inside an env that was created with a different version of mock (group names have changed from mock to mockbuild or vice versa)

On Jun 17, 2018 22:53, "Nir Soffer" <nsoffer@redhat.com> wrote:

2 Fedora builds failed recently with this error:

19:40:34 ERROR: Command failed: 19:40:34 # /usr/sbin/groupadd -g 1000 mock

See latest builds of this patch:
https://gerrit.ovirt.org/#/c/91834/

I merged the patch regardless, but please take a look.