[Reason: Bug in Code] Failure in "qa/specs/features/browser_ui/3_create/merge_request/rebase_merge_request_spec.rb:6"

This failed in staging:

https://gitlab.com/gitlab-org/quality/staging/-/jobs/254951339

as well as in infra deployer pipeline:

https://ops.gitlab.net/gitlab-com/gl-infra/deployer/-/jobs/566594

Failures:

  1) Create Merge request rebasing user rebases source branch of merge request
     Failure/Error: expect(merge_request).to have_content('Needs rebasing')
       expected to find text "Needs rebasing" in "500 Whoops, something went wrong on our end. Try refreshing the page, or going back and attempting the action again. Please contact your GitLab administrator if this problem persists. Go back"
     # ./qa/specs/features/browser_ui/3_create/merge_request/rebase_merge_request_spec.rb:34:in `block (4 levels) in <module:QA>'
     # ./qa/scenario/actable.rb:16:in `perform'
     # ./qa/specs/features/browser_ui/3_create/merge_request/rebase_merge_request_spec.rb:33:in `block (3 levels) in <module:QA>'

Screenshot:

rebase_merge_request_spec.rb_2019-07-19-04-38-34.009.html

Reproduced against staging when run from local:

GITLAB_ADMIN_USERNAME="quality+qa_bot@gitlab.com" GITLAB_ADMIN_PASSWORD="<gitlab_admin_password>" GITLAB_QA_ADMIN_ACCESS_TOKEN="<gitlab_qa_admin_accesas_token>" GITLAB_USERNAME="gitlab-qa" GITLAB_PASSWORD="<gitlab_password>" GITLAB_QA_ACCESS_TOKEN="<gitlab_qa_access_token>" QA_DEBUG=true CHROME_HEADLESS=false bin/qa Test::Instance::All https://staging.gitlab.com -- qa/specs/features/browser_ui/3_create/merge_request/rebase_merge_request_spec.rb:6

However, I was able to see the page upon refreshing:

https://staging.gitlab.com/gitlab-qa-sandbox-group/qa-test-2019-07-19-11-49-21-401654cd9903aadc/only-fast-forward-050c0fc212537a2d/merge_requests/1