Usually fixed by refreshing (re-sending POST) the browser multiple times.
# sudo -u git -H bundle exec rake gitlab:env:info RAILS_ENV=production
System information
System: Debian 7.8
Current User: git
Using RVM: no
Ruby Version: 2.1.5p273
Gem Version: 2.2.2
Bundler Version:1.8.2
Rake Version: 10.3.2
Sidekiq Version:3.3.0
GitLab information
Version: 7.8.0
Revision: 44c69cb
Directory: /home/git/gitlab
DB Adapter: postgresql
Using LDAP: no
Using Omniauth: no
GitLab Shell
Version: 2.5.3
Repositories: /home/git/repositories/
Hooks: /home/git/gitlab-shell/hooks/
Git: /usr/bin/git
The server itself has 4GB RAM available and multicore cpu. The error comes instantly so it does not seem to be an memory or timeout problem.
I posted the bug here: https://bugs.ruby-lang.org/issues/10872 but it was closed as invalid.
I have no clue how ruby works so no idea what I am looking at or looking for.
For future reference: turns out GitLab does not run on Debian 7 32Bit - I can not say for sure, but doubt it has to do with the versions in Debian's 7 repository (which are in general older) as I compiled most of the stuff and with gem it anyway got the versions as defined by GitLab.
Very likely GitLab (or gems it is using) does not currently work on a 32Bit system.