$ centpkg clone xz
Cloning into 'xz'...
remote: Enumerating objects: 309, done.
remote: Counting objects: 100% (15/15), done.
remote: Compressing objects: 100% (11/11), done.
remote: Total 309 (delta 3), reused 12 (delta 2), pack-reused 294
Receiving objects: 100% (309/309), 49.50 KiB | 3.54 MiB/s, done.
Resolving deltas: 100% (137/137), done.

$ cd xz

$ centpkg fork
Repo 'https://gitlab.com/hhorak/centos_rpms_xz' already exists.
Adding as remote 'hhorak'.

$ echo >>*spec
$ git commit -am "useless change"
[c9s 2064fe7] useless change
 1 file changed, 1 insertion(+)
$ git checkout -b useless-change
Switched to a new branch 'useless-change'

$ git push --set-upstream hhorak useless-change
Could not execute pre_push_check: Branchname: useless-change is not valid
error: failed to push some refs to 'git+ssh://gitlab.com/hhorak/centos_rpms_xz.git'