v10.1.0 Triggering build results in 500 error

Summary

(Summarize the bug encountered concisely)

Triggering a build results in

fatal: unable to access 'https://gitlab-ci-token:xxxxxxxxxxxxxxxxxxxx@gitlab.matty-inc.tk/vakantiespel/vks-backend.git/': The requested URL returned error: 500

Relevant logs and/or screenshots

(Paste any relevant logs - please use code blocks (```) to format console output, logs, and code as it's very hard to read otherwise.)

Running with gitlab-ci-multi-runner 9.5.1 (96b34cc)
  on Docker VKS runner (2a08c017)
Using Docker executor with image mgimatty/ubuntu-gitlab-ci ...
Using docker image sha256:eef1dd57497f1eb84f9f8552c57b205b6a8c121ca4a1fc0966f466dfeb377593 for predefined container...
Pulling docker image mgimatty/ubuntu-gitlab-ci ...
Using docker image mgimatty/ubuntu-gitlab-ci ID=sha256:b3f0143817d5874e675bf2d39feac7a08958a8fe3c75b3c8c2f41fdd95a67960 for build container...
Running on runner-2a08c017-project-8-concurrent-0 via matty-inc...
Cloning repository...
Cloning into '/builds/vakantiespel/vks-backend'...
remote: Internal server error
fatal: unable to access 'https://gitlab-ci-token:xxxxxxxxxxxxxxxxxxxx@gitlab.matty-inc.tk/vakantiespel/vks-backend.git/': The requested URL returned error: 500
ERROR: Job failed: exit code 1

Output of checks

(If you are reporting a bug on GitLab.com, write: This bug happens on GitLab.com)

Results of GitLab environment info

Expand for output related to GitLab environment info

(For installations with omnibus-gitlab package run and paste the output of:
sudo gitlab-rake gitlab:env:info)
(For installations from source run and paste the output of:
sudo -u git -H bundle exec rake gitlab:env:info RAILS_ENV=production)
System information
System:         Ubuntu 16.04
Current User:   git
Using RVM:      no
Ruby Version:   2.3.3p222
Gem Version:    2.5.2
Bundler Version:1.15.4
Rake Version:   12.1.0
Redis Version:  3.0.6
Git Version:    2.7.4
Sidekiq Version:5.0.4
Go Version:     go1.8.3 linux/amd64
GitLab information
Version:        10.1.0
Revision:       5a695c4
Directory:      /home/git/gitlab
DB Adapter:     mysql2
URL:            https://gitlab.matty-inc.tk
HTTP Clone URL: https://gitlab.matty-inc.tk/some-group/some-project.git
SSH Clone URL:  git@gitlab.matty-inc.tk:some-group/some-project.git
Using LDAP:     no
Using Omniauth: no
GitLab Shell
Version:        5.9.3
Repository storage paths:

• default: /home/git/repositories Hooks: /home/git/gitlab-shell/hooks Git: /usr/bin/git

Results of GitLab application Check

Expand for output related to the GitLab application check

(For installations with omnibus-gitlab package run and paste the output of:
sudo gitlab-rake gitlab:check SANITIZE=true)
(For installations from source run and paste the output of:
sudo -u git -H bundle exec rake gitlab:check RAILS_ENV=production SANITIZE=true)
(we will only investigate if the tests are passing)
Checking GitLab Shell ...
GitLab Shell version >= 5.9.3 ? ... OK (5.9.3)
Repo base directory exists?
default... yes
Repo storage directories are symlinks?
default... no
Repo paths owned by git:root, or git:git?
default... yes
Repo paths access is drwxrws---?
default... yes
hooks directories in repos are links: ...
2/1 ... ok
3/3 ... ok
4/4 ... ok
5/5 ... ok
6/6 ... ok
6/8 ... ok
7/9 ... ok
6/10 ... ok
4/11 ... ok
6/13 ... ok
16/16 ... ok
4/17 ... ok
6/18 ... ok
6/19 ... ok
6/20 ... ok
6/21 ... repository is empty
6/22 ... repository is empty
Running /home/git/gitlab-shell/bin/check
Check GitLab API access: OK
Redis available via internal API: OK
Access to /home/git/.ssh/authorized_keys: OK
gitlab-shell self-check successful
Checking GitLab Shell ... Finished
Checking Sidekiq ...
Running? ... yes
Number of Sidekiq processes ... 1
Checking Sidekiq ... Finished
Reply by email is disabled in config/gitlab.yml
Checking LDAP ...
LDAP is disabled in config/gitlab.yml
Checking LDAP ... Finished
Checking GitLab ...
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? ... yes
Uploads directory tmp has correct permissions? ... yes
Init script exists? ... yes
Init script up-to-date? ... yes
Projects have namespace: ...
2/1 ... yes
3/3 ... yes
4/4 ... yes
5/5 ... yes
6/6 ... yes
6/8 ... yes
7/9 ... yes
6/10 ... yes
4/11 ... yes
6/13 ... yes
16/16 ... yes
4/17 ... yes
6/18 ... yes
6/19 ... yes
6/20 ... yes
6/21 ... yes
6/22 ... yes
Redis version >= 2.8.0? ... yes
Ruby version >= 2.3.3 ? ... yes (2.3.3)
Git version >= 2.7.3 ? ... yes (2.7.4)
Git user has default SSH configuration? ... yes
Active users: ... 12
Checking GitLab ... Finished

Possible fixes

(If you can, link to the line of code that might be responsible for the problem)