Weird unhelpful email

I just received an e-mail from my gitlab (13.11.1-ee) instance:

bundler: failed to load command: rake (/opt/gitlab/embedded/bin/rake)
Bundler::GemNotFound: Could not find gem 'brakeman (~> 4.2)' in any of the gem sources listed in your Gemfile.
  /opt/gitlab/embedded/lib/ruby/site_ruby/2.7.0/bundler/resolver.rb:290:in `block in verify_gemfile_dependencies_are_found!'
  /opt/gitlab/embedded/lib/ruby/site_ruby/2.7.0/bundler/resolver.rb:258:in `each'
  /opt/gitlab/embedded/lib/ruby/site_ruby/2.7.0/bundler/resolver.rb:258:in `verify_gemfile_dependencies_are_found!'
  /opt/gitlab/embedded/lib/ruby/site_ruby/2.7.0/bundler/resolver.rb:49:in `start'
  /opt/gitlab/embedded/lib/ruby/site_ruby/2.7.0/bundler/resolver.rb:22:in `resolve'
  /opt/gitlab/embedded/lib/ruby/site_ruby/2.7.0/bundler/definition.rb:258:in `resolve'
  /opt/gitlab/embedded/lib/ruby/site_ruby/2.7.0/bundler/definition.rb:170:in `specs'
  /opt/gitlab/embedded/lib/ruby/site_ruby/2.7.0/bundler/definition.rb:237:in `specs_for'
  /opt/gitlab/embedded/lib/ruby/site_ruby/2.7.0/bundler/definition.rb:226:in `requested_specs'
  /opt/gitlab/embedded/lib/ruby/site_ruby/2.7.0/bundler/runtime.rb:101:in `block in definition_method'
  /opt/gitlab/embedded/lib/ruby/site_ruby/2.7.0/bundler/runtime.rb:20:in `setup'
  /opt/gitlab/embedded/lib/ruby/site_ruby/2.7.0/bundler.rb:149:in `setup'
  /opt/gitlab/embedded/lib/ruby/site_ruby/2.7.0/bundler/setup.rb:20:in `block in <top (required)>'
  /opt/gitlab/embedded/lib/ruby/site_ruby/2.7.0/bundler/ui/shell.rb:136:in `with_level'
  /opt/gitlab/embedded/lib/ruby/site_ruby/2.7.0/bundler/ui/shell.rb:88:in `silence'
  /opt/gitlab/embedded/lib/ruby/site_ruby/2.7.0/bundler/setup.rb:20:in `<top (required)>'

This is literally the entire contents of the e-mail.

I have no clue, whatsoever, this is and where to start looking. Googling for brakeman etc. resulted in no useful information. I have updated my gitlab earlier today so that might be related.

Luckily this is in a VM for personal usage and not a sizeable enterprise installation.