Can't import from GitHub - namespace already taken

Summary

When attempting to import a project from GitHub, the error message "This namespace is already taken" is showed. Attempting to change the namespace produces the same error, no matter what is selected. The user I'm importing with has full admin rights and is the owner of the target namespace.

Steps to reproduce

Set up OmniAuth with Google. (Not sure if this is relevant, but it seemed related judging from issue https://gitlab.com/gitlab-org/gitlab-ee/issues/708)

Attempt to import a private project from GitHub.

What is the current bug behavior?

The error message "This namespace is already taken" is showed. Attempting to change the namespace produces the same error, no matter what is selected.

What is the expected correct behavior?

Project should be imported.

Results of GitLab environment info

Expand for output related to GitLab environment info

System information
System:         Ubuntu 16.04
Proxy:          no
Current User:   git
Using RVM:      no
Ruby Version:   2.3.5p376
Gem Version:    2.6.13
Bundler Version:1.13.7
Rake Version:   12.3.0
Redis Version:  3.2.11
Git Version:    2.14.3
Sidekiq Version:5.0.4
Go Version:     unknown
GitLab information
Version:        10.3.4-ee
Revision:       00c14ad
Directory:      /opt/gitlab/embedded/service/gitlab-rails
DB Adapter:     postgresql
DB Version:     9.6.5
URL:            https://ilabs.se
HTTP Clone URL: https://ilabs.se/some-group/some-project.git
SSH Clone URL:  git@ilabs.se:some-group/some-project.git
Elasticsearch:  no
Geo:            no
Using LDAP:     no
Using Omniauth: yes
Omniauth Providers: google_oauth2
GitLab Shell
Version:        5.10.2
Repository storage paths:
- default:      /var/opt/gitlab/git-data/repositories
Hooks:          /opt/gitlab/embedded/service/gitlab-shell/hooks
Git:            /opt/gitlab/embedded/bin/git

Results of GitLab application Check

Expand for output related to the GitLab application check

Checking GitLab Shell ...
GitLab Shell version >= 5.10.2 ? ... OK (5.10.2)
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: ...
2/2 ... ok
2/3 ... /opt/gitlab/embedded/service/gitlab-rails/lib/gitlab/git/repository.rb:24: warning: already initialized constant Gitlab::Git::Repository::GITALY_INTERNAL_URL
/opt/gitlab/embedded/service/gitlab-rails/lib/gitlab/git/repository.rb:21: warning: previous definition of GITALY_INTERNAL_URL was here
ok
2/4 ... ok
2/5 ... ok
Running /opt/gitlab/embedded/service/gitlab-shell/bin/check
Check GitLab API access: OK
Redis available via internal API: OK
Access to /var/opt/gitlab/.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? ... skipped (no tmp uploads folder yet)
Init script exists? ... skipped (omnibus-gitlab has no init script)
Init script up-to-date? ... skipped (omnibus-gitlab has no init script)
Projects have namespace: ...
2/2 ... yes
2/3 ... yes
2/4 ... yes
2/5 ... yes
Redis version >= 2.8.0? ... yes
Ruby version >= 2.3.5 ? ... yes (2.3.5)
Git version >= 2.7.3 ? ... yes (2.14.3)
Git user has default SSH configuration? ... yes
Active users: ... 1
Elasticsearch version 5.1 - 5.5? ... skipped (elasticsearch is disabled)
Checking GitLab ... Finished