Gitaly fails to start in 11.9.1: Could not find abstract_type-0.0.7 gem

Summary

After upgrading to 11.9.1 and attempting to start Gitlab. Gitaly fails to start complaining that it cannot find the gem abstract_type-0.0.7.

Steps to reproduce

Upgrade from 11.8.3 to 11.9.1, migrate configuration, and attempt to start Gitlab.

What is the current bug behavior?

Gitaly fails to start. gitaly.log has the following output:

time="2019-04-02T01:50:57-04:00" level=info msg="Starting Gitaly" version="Gitaly, version 1.27.1"
time="2019-04-02T01:50:57-04:00" level=warning msg="git path not configured. Using default path resolution" resolvedPath=/usr/bin/git
time="2019-04-02T01:50:57-04:00" level=warning msg="git path not configured. Using default path resolution" resolvedPath=/usr/bin/git
/usr/lib64/ruby/gems/2.5.0/gems/bundler-1.17.3/lib/bundler/spec_set.rb:91:in `block in materialize': Could not find abstract_type-0.0.7 in any of the sources (Bundler::GemNotFound)
        from /usr/lib64/ruby/gems/2.5.0/gems/bundler-1.17.3/lib/bundler/spec_set.rb:85:in `map!'
        from /usr/lib64/ruby/gems/2.5.0/gems/bundler-1.17.3/lib/bundler/spec_set.rb:85:in `materialize'
        from /usr/lib64/ruby/gems/2.5.0/gems/bundler-1.17.3/lib/bundler/definition.rb:170:in `specs'
        from /usr/lib64/ruby/gems/2.5.0/gems/bundler-1.17.3/lib/bundler/definition.rb:237:in `specs_for'
        from /usr/lib64/ruby/gems/2.5.0/gems/bundler-1.17.3/lib/bundler/definition.rb:226:in `requested_specs'
        from /usr/lib64/ruby/gems/2.5.0/gems/bundler-1.17.3/lib/bundler/runtime.rb:108:in `block in definition_method'
        from /usr/lib64/ruby/gems/2.5.0/gems/bundler-1.17.3/lib/bundler/runtime.rb:20:in `setup'
        from /usr/lib64/ruby/gems/2.5.0/gems/bundler-1.17.3/lib/bundler.rb:107:in `setup'
        from /usr/lib64/ruby/gems/2.5.0/gems/bundler-1.17.3/lib/bundler/setup.rb:20:in `<top (required)>'
        from /usr/lib64/ruby/site_ruby/2.5.0/rubygems/core_ext/kernel_require.rb:54:in `require'
        from /usr/lib64/ruby/site_ruby/2.5.0/rubygems/core_ext/kernel_require.rb:54:in `require'
time="2019-04-02T01:50:57-04:00" level=fatal msg="load config" config_path=/etc/gitaly/config.toml error="load linguist colors: exit status 1; stderr: \"\""

What is the expected correct behavior?

Gitlab starts correctly.

Output of checks

Results of GitLab environment info

# sudo -u git -H bundle exec rake gitlab:env:info RAILS_ENV=production

System information
System:         Gentoo 2.6
Current User:   git
Using RVM:      no
Ruby Version:   2.5.5p157
Gem Version:    3.0.3
Bundler Version:1.17.3
Rake Version:   12.3.2
Redis Version:  4.0.10
Git Version:    2.21.0
Sidekiq Version:5.2.5
Go Version:     go1.12.1 linux/amd64

GitLab information
Version:        11.9.1
Revision:       86f0b5dd4d
Directory:      /opt/gitlabhq-11.9
DB Adapter:     mysql2
URL:            https://[redacted]
HTTP Clone URL: https://[redacted]/some-group/some-project.git
SSH Clone URL:  git@[redacted]:some-group/some-project.git
Using LDAP:     no
Using Omniauth: no

GitLab Shell
Version:        8.7.1
Repository storage paths:
- default:      /var/lib/git/repositories
GitLab Shell path:              /var/lib/gitlab-shell
Git:            /usr/bin/git

Results of GitLab application Check

# sudo -u git -H bundle exec rake gitlab:check RAILS_ENV=production
Checking GitLab subtasks ...

Checking GitLab Shell ...

GitLab Shell: ... GitLab Shell version >= 8.7.1 ? ... OK (8.7.1)
Running /var/lib/gitlab-shell/bin/check
Check GitLab API access: OK
Redis available via internal API: OK

Access to /var/lib/git/.ssh/authorized_keys: OK
gitlab-shell self-check successful

Checking GitLab Shell ... Finished

Checking Gitaly ...

Gitaly: ... default ... FAIL: 14:Connect Failed

Checking Gitaly ... Finished

Checking Sidekiq ...

Sidekiq: ... Running? ... no
  Try fixing it:
  sudo -u git -H RAILS_ENV=production bin/background_jobs start
  For more information see:
  doc/install/installation.md in section "Install Init Script"
  see log/sidekiq.log for possible errors
  Please fix the error above and rerun the checks.

Checking Sidekiq ... Finished

Checking Incoming Email ...

Incoming Email: ... Reply by email is disabled in config/gitlab.yml

Checking Incoming Email ... Finished

Checking LDAP ...

LDAP: ... LDAP is disabled in config/gitlab.yml

Checking LDAP ... Finished

Checking GitLab App ...

Git configured correctly? ... yes
Database config exists? ... yes
All migrations up? ... yes
Database contains orphaned GroupMembers? ... no
GitLab config exists? ... yes
GitLab config up to date? ... yes
Log directory writable? ... yes
Tmp directory writable? ... yes
Uploads directory exists? ... yes
Uploads directory has correct permissions? ... no
  Try fixing it:
  sudo chmod 700 /opt/gitlabhq-11.9/public/uploads
  For more information see:
  doc/install/installation.md in section "GitLab"
  Please fix the error above and rerun the checks.
Uploads directory tmp has correct permissions? ... skipped (no tmp uploads folder yet)
Projects have namespace: ...
[redacted] ... yes
[redacted] ... yes
[redacted] ... yes
[redacted] ... yes
...
Redis version >= 2.8.0? ... yes
Ruby version >= 2.3.5 ? ... yes (2.5.5)
Git version >= 2.18.0 ? ... yes (2.21.0)
Git user has default SSH configuration? ... no
  Try fixing it:
  mkdir ~/gitlab-check-backup-1554185059
  sudo mv /var/lib/git/.ssh/id_rsa.pub ~/gitlab-check-backup-1554185059
  sudo mv /var/lib/git/.ssh/id_rsa ~/gitlab-check-backup-1554185059
  For more information see:
  doc/ssh/README.md in section "SSH on the GitLab server"
  Please fix the error above and rerun the checks.
Active users: ... 2

Checking GitLab App ... Finished


Checking GitLab subtasks ... Finished