Migration fails with "Foreign key constraint is incorrectly formed"

Summary

Migrating to 9.1.4 db migration failure

Steps to reproduce

Be on version:

GitLab 7.14.1

GitLab Shell 2.6.4

GitLab API v3

Ruby 2.0.0p384

Rails 4.1.11

Mysql: Server version: 10.0.14-MariaDB-1~trusty-log mariadb.org binary distribution

When you upgrade and run: bundle exec rake db:migrate RAILS_ENV=production

What is the current bug behavior?

(What actually happens)

What is the expected correct behavior?

Success!

Relevant logs and/or screenshots

== 20160415062917 CreatePersonalAccessTokens: migrating ======================= -- create_table(:personal_access_tokens) rake aborted! StandardError: An error has occurred, all later migrations canceled:

Mysql2::Error: Can't create table gitlabhq_production.#sql-4c1_24f (errno: 150 "Foreign key constraint is incorrectly formed"): ALTER TABLE personal_access_tokens ADD CON STRAINT fk_rails_08903b8f38 FOREIGN KEY (user_id) REFERENCES users (id)