I got this when pushing a new release branch for gnome-characters: $ git push origin gnome-3-26 Total 0 (delta 0), reused 0 (delta 0) remote: remote: To create a merge request for gnome-3-26, visit: remote: https://gitlab.gnome.org/GNOME/gnome-characters/merge_requests/new?merge_request%5Bsource_branch%5D=gnome-3-26 remote: remote: Traceback (most recent call last): remote: File "/home/admin/bin/git/gnome-post-receive-email", line 1006, in <module> remote: main() remote: File "/home/admin/bin/git/gnome-post-receive-email", line 995, in main remote: changes.append(make_change(items[0], items[1], items[2])) remote: File "/home/admin/bin/git/gnome-post-receive-email", line 925, in make_change remote: return make(BranchCreation) remote: File "/home/admin/bin/git/gnome-post-receive-email", line 895, in make remote: return cls(refname, oldrev, newrev, *args) remote: File "/home/admin/bin/git/gnome-post-receive-email", line 409, in __init__ remote: '%s@src.gnome.org' % os.environ['USER'] remote: File "/usr/lib64/python2.7/UserDict.py", line 23, in __getitem__ remote: raise KeyError(key) remote: KeyError: 'USER' To gitlab.gnome.org:GNOME/gnome-characters.git * [new branch] gnome-3-26 -> gnome-3-26