Gemfile missing sqlite3 ref: upgrade from 3.0 to 3.1 fails

Created by: mkarau

The Gemfile contains a reference to sqlite instead of sqlite3.

Original Gemfile snippet(Fails):

# Supported DBs
gem "sqlite3", group: :sqlite
gem "mysql2", group: :mysql
gem "pg", group: :postgres

This causes the following step in the upgrade to fail.

# Migrate db
sudo -u gitlab -H bundle exec rake db:migrate RAILS_ENV=production

Fails with:

rake aborted!
Please install the sqlite3 adapter: `gem install activerecord-sqlite3-adapter` (sqlite3 is not part of the bundle. Add it to Gemfile.)
/home/gitlab/gitlab/vendor/bundle/ruby/1.9.1/gems/activerecord-3.2.9/lib/active_record/connection_adapters/sqlite3_adapter.rb:3:in `<top (required)>'
....
....

Modified Gemfile snippet (Sucessfully Builds):

# Supported DBs
gem "sqlite3", group: :sqlite3
gem "mysql2", group: :mysql
gem "pg", group: :postgres