Get error when upgrade from 7.5.0rc to 7.6

Hello,

I'm using gitlab 7.5.0rc, I upgrading gitlab to 7.6 using tutorial: https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/update/7.5-to-7.6.md

After run:

sudo -u git -H bundle exec rake db:migrate RAILS_ENV=production

I get error:

** Invoke db:migrate (first_time)
** Invoke environment (first_time)
** Execute environment
** Invoke db:load_config (first_time)
** Execute db:load_config
** Execute db:migrate
== 20141121161704 AddIdentityTable: migrating =================================
-- create_table(:identities)
   -> 0.1214s
-- add_index(:identities, :user_id)
   -> 0.1660s
-- execute("INSERT INTO identities (provider, extern_uid, user_id)\nSELECT provider, extern_uid, id FROM users\nWHERE provider IS NOT NULL\n")
   -> 0.0518s
-- remove_column(:users, :extern_uid)
rake aborted!
StandardError: An error has occurred, all later migrations canceled:

Mysql2::Error: Duplicate entry 'ldap' for key 'index_users_on_extern_uid_and_provider': ALTER TABLE `users` DROP `extern_uid`/home/git/gitlab/vendor/bundle/ruby/2.1.0/gems/activerecord-4.1.1/lib/active_record/connection_adapters/abstract_mysql_adapter.rb:301:in `query'
/home/git/gitlab/vendor/bundle/ruby/2.1.0/gems/activerecord-4.1.1/lib/active_record/connection_adapters/abstract_mysql_adapter.rb:301:in `block in execute'
/home/git/gitlab/vendor/bundle/ruby/2.1.0/gems/activerecord-4.1.1/lib/active_record/connection_adapters/abstract_adapter.rb:373:in `block in log'
/home/git/gitlab/vendor/bundle/ruby/2.1.0/gems/activesupport-4.1.1/lib/active_support/notifications/instrumenter.rb:20:in `instrument'
/home/git/gitlab/vendor/bundle/ruby/2.1.0/gems/activerecord-4.1.1/lib/active_record/connection_adapters/abstract_adapter.rb:367:in `log'
/home/git/gitlab/vendor/bundle/ruby/2.1.0/gems/activerecord-4.1.1/lib/active_record/connection_adapters/abstract_mysql_adapter.rb:301:in `execute'
/home/git/gitlab/vendor/bundle/ruby/2.1.0/gems/activerecord-4.1.1/lib/active_record/connection_adapters/mysql2_adapter.rb:228:in `execute'
/home/git/gitlab/vendor/bundle/ruby/2.1.0/gems/activerecord-4.1.1/lib/active_record/connection_adapters/abstract/schema_statements.rb:397:in `remove_column'
/home/git/gitlab/vendor/bundle/ruby/2.1.0/gems/activerecord-4.1.1/lib/active_record/migration.rb:649:in `block in method_missing'
/home/git/gitlab/vendor/bundle/ruby/2.1.0/gems/activerecord-4.1.1/lib/active_record/migration.rb:621:in `block in say_with_time'
/usr/local/lib/ruby/2.1.0/benchmark.rb:279:in `measure'
/home/git/gitlab/vendor/bundle/ruby/2.1.0/gems/activerecord-4.1.1/lib/active_record/migration.rb:621:in `say_with_time'
/home/git/gitlab/vendor/bundle/ruby/2.1.0/gems/activerecord-4.1.1/lib/active_record/migration.rb:641:in `method_missing'
/home/git/gitlab/db/migrate/20141121161704_add_identity_table.rb:17:in `up'
/home/git/gitlab/vendor/bundle/ruby/2.1.0/gems/activerecord-4.1.1/lib/active_record/migration.rb:598:in `exec_migration'
/home/git/gitlab/vendor/bundle/ruby/2.1.0/gems/activerecord-4.1.1/lib/active_record/migration.rb:579:in `block (2 levels) in migrate'
/usr/local/lib/ruby/2.1.0/benchmark.rb:279:in `measure'
/home/git/gitlab/vendor/bundle/ruby/2.1.0/gems/activerecord-4.1.1/lib/active_record/migration.rb:578:in `block in migrate'
/home/git/gitlab/vendor/bundle/ruby/2.1.0/gems/activerecord-4.1.1/lib/active_record/connection_adapters/abstract/connection_pool.rb:294:in `with_connection'
/home/git/gitlab/vendor/bundle/ruby/2.1.0/gems/activerecord-4.1.1/lib/active_record/migration.rb:577:in `migrate'
/home/git/gitlab/vendor/bundle/ruby/2.1.0/gems/activerecord-4.1.1/lib/active_record/migration.rb:752:in `migrate'
/home/git/gitlab/vendor/bundle/ruby/2.1.0/gems/activerecord-4.1.1/lib/active_record/migration.rb:992:in `block in execute_migration_in_transaction'
/home/git/gitlab/vendor/bundle/ruby/2.1.0/gems/activerecord-4.1.1/lib/active_record/migration.rb:1040:in `ddl_transaction'
/home/git/gitlab/vendor/bundle/ruby/2.1.0/gems/activerecord-4.1.1/lib/active_record/migration.rb:991:in `execute_migration_in_transaction'
/home/git/gitlab/vendor/bundle/ruby/2.1.0/gems/activerecord-4.1.1/lib/active_record/migration.rb:953:in `block in migrate'
/home/git/gitlab/vendor/bundle/ruby/2.1.0/gems/activerecord-4.1.1/lib/active_record/migration.rb:949:in `each'
/home/git/gitlab/vendor/bundle/ruby/2.1.0/gems/activerecord-4.1.1/lib/active_record/migration.rb:949:in `migrate'
/home/git/gitlab/vendor/bundle/ruby/2.1.0/gems/activerecord-4.1.1/lib/active_record/migration.rb:807:in `up'
/home/git/gitlab/vendor/bundle/ruby/2.1.0/gems/activerecord-4.1.1/lib/active_record/migration.rb:785:in `migrate'
/home/git/gitlab/vendor/bundle/ruby/2.1.0/gems/activerecord-4.1.1/lib/active_record/railties/databases.rake:34:in `block (2 levels) in <top (required)>'
/home/git/gitlab/vendor/bundle/ruby/2.1.0/gems/rake-10.3.2/lib/rake/task.rb:240:in `call'
/home/git/gitlab/vendor/bundle/ruby/2.1.0/gems/rake-10.3.2/lib/rake/task.rb:240:in `block in execute'
/home/git/gitlab/vendor/bundle/ruby/2.1.0/gems/rake-10.3.2/lib/rake/task.rb:235:in `each'
/home/git/gitlab/vendor/bundle/ruby/2.1.0/gems/rake-10.3.2/lib/rake/task.rb:235:in `execute'
/home/git/gitlab/vendor/bundle/ruby/2.1.0/gems/rake-10.3.2/lib/rake/task.rb:179:in `block in invoke_with_call_chain'
/usr/local/lib/ruby/2.1.0/monitor.rb:211:in `mon_synchronize'
/home/git/gitlab/vendor/bundle/ruby/2.1.0/gems/rake-10.3.2/lib/rake/task.rb:172:in `invoke_with_call_chain'
/home/git/gitlab/vendor/bundle/ruby/2.1.0/gems/rake-10.3.2/lib/rake/task.rb:165:in `invoke'
/home/git/gitlab/vendor/bundle/ruby/2.1.0/gems/rake-10.3.2/lib/rake/application.rb:150:in `invoke_task'
/home/git/gitlab/vendor/bundle/ruby/2.1.0/gems/rake-10.3.2/lib/rake/application.rb:106:in `block (2 levels) in top_level'
/home/git/gitlab/vendor/bundle/ruby/2.1.0/gems/rake-10.3.2/lib/rake/application.rb:106:in `each'
/home/git/gitlab/vendor/bundle/ruby/2.1.0/gems/rake-10.3.2/lib/rake/application.rb:106:in `block in top_level'
/home/git/gitlab/vendor/bundle/ruby/2.1.0/gems/rake-10.3.2/lib/rake/application.rb:115:in `run_with_threads'
/home/git/gitlab/vendor/bundle/ruby/2.1.0/gems/rake-10.3.2/lib/rake/application.rb:100:in `top_level'
/home/git/gitlab/vendor/bundle/ruby/2.1.0/gems/rake-10.3.2/lib/rake/application.rb:78:in `block in run'
/home/git/gitlab/vendor/bundle/ruby/2.1.0/gems/rake-10.3.2/lib/rake/application.rb:176:in `standard_exception_handling'
/home/git/gitlab/vendor/bundle/ruby/2.1.0/gems/rake-10.3.2/lib/rake/application.rb:75:in `run'
/home/git/gitlab/vendor/bundle/ruby/2.1.0/gems/rake-10.3.2/bin/rake:33:in `<top (required)>'
/home/git/gitlab/vendor/bundle/ruby/2.1.0/bin/rake:23:in `load'
/home/git/gitlab/vendor/bundle/ruby/2.1.0/bin/rake:23:in `<main>'
ActiveRecord::RecordNotUnique: Mysql2::Error: Duplicate entry 'ldap' for key 'index_users_on_extern_uid_and_provider': ALTER TABLE `users` DROP `extern_uid`
/home/git/gitlab/vendor/bundle/ruby/2.1.0/gems/activerecord-4.1.1/lib/active_record/connection_adapters/abstract_mysql_adapter.rb:301:in `query'
/home/git/gitlab/vendor/bundle/ruby/2.1.0/gems/activerecord-4.1.1/lib/active_record/connection_adapters/abstract_mysql_adapter.rb:301:in `block in execute'
/home/git/gitlab/vendor/bundle/ruby/2.1.0/gems/activerecord-4.1.1/lib/active_record/connection_adapters/abstract_adapter.rb:373:in `block in log'
/home/git/gitlab/vendor/bundle/ruby/2.1.0/gems/activesupport-4.1.1/lib/active_support/notifications/instrumenter.rb:20:in `instrument'
/home/git/gitlab/vendor/bundle/ruby/2.1.0/gems/activerecord-4.1.1/lib/active_record/connection_adapters/abstract_adapter.rb:367:in `log'
/home/git/gitlab/vendor/bundle/ruby/2.1.0/gems/activerecord-4.1.1/lib/active_record/connection_adapters/abstract_mysql_adapter.rb:301:in `execute'
/home/git/gitlab/vendor/bundle/ruby/2.1.0/gems/activerecord-4.1.1/lib/active_record/connection_adapters/mysql2_adapter.rb:228:in `execute'
/home/git/gitlab/vendor/bundle/ruby/2.1.0/gems/activerecord-4.1.1/lib/active_record/connection_adapters/abstract/schema_statements.rb:397:in `remove_column'
/home/git/gitlab/vendor/bundle/ruby/2.1.0/gems/activerecord-4.1.1/lib/active_record/migration.rb:649:in `block in method_missing'
/home/git/gitlab/vendor/bundle/ruby/2.1.0/gems/activerecord-4.1.1/lib/active_record/migration.rb:621:in `block in say_with_time'
/usr/local/lib/ruby/2.1.0/benchmark.rb:279:in `measure'
/home/git/gitlab/vendor/bundle/ruby/2.1.0/gems/activerecord-4.1.1/lib/active_record/migration.rb:621:in `say_with_time'
/home/git/gitlab/vendor/bundle/ruby/2.1.0/gems/activerecord-4.1.1/lib/active_record/migration.rb:641:in `method_missing'
/home/git/gitlab/db/migrate/20141121161704_add_identity_table.rb:17:in `up'
/home/git/gitlab/vendor/bundle/ruby/2.1.0/gems/activerecord-4.1.1/lib/active_record/migration.rb:598:in `exec_migration'
/home/git/gitlab/vendor/bundle/ruby/2.1.0/gems/activerecord-4.1.1/lib/active_record/migration.rb:579:in `block (2 levels) in migrate'
/usr/local/lib/ruby/2.1.0/benchmark.rb:279:in `measure'
/home/git/gitlab/vendor/bundle/ruby/2.1.0/gems/activerecord-4.1.1/lib/active_record/migration.rb:578:in `block in migrate'
/home/git/gitlab/vendor/bundle/ruby/2.1.0/gems/activerecord-4.1.1/lib/active_record/connection_adapters/abstract/connection_pool.rb:294:in `with_connection'
/home/git/gitlab/vendor/bundle/ruby/2.1.0/gems/activerecord-4.1.1/lib/active_record/migration.rb:577:in `migrate'
/home/git/gitlab/vendor/bundle/ruby/2.1.0/gems/activerecord-4.1.1/lib/active_record/migration.rb:752:in `migrate'
/home/git/gitlab/vendor/bundle/ruby/2.1.0/gems/activerecord-4.1.1/lib/active_record/migration.rb:992:in `block in execute_migration_in_transaction'
/home/git/gitlab/vendor/bundle/ruby/2.1.0/gems/activerecord-4.1.1/lib/active_record/migration.rb:1040:in `ddl_transaction'
/home/git/gitlab/vendor/bundle/ruby/2.1.0/gems/activerecord-4.1.1/lib/active_record/migration.rb:991:in `execute_migration_in_transaction'
/home/git/gitlab/vendor/bundle/ruby/2.1.0/gems/activerecord-4.1.1/lib/active_record/migration.rb:953:in `block in migrate'
/home/git/gitlab/vendor/bundle/ruby/2.1.0/gems/activerecord-4.1.1/lib/active_record/migration.rb:949:in `each'
/home/git/gitlab/vendor/bundle/ruby/2.1.0/gems/activerecord-4.1.1/lib/active_record/migration.rb:949:in `migrate'
/home/git/gitlab/vendor/bundle/ruby/2.1.0/gems/activerecord-4.1.1/lib/active_record/migration.rb:807:in `up'
/home/git/gitlab/vendor/bundle/ruby/2.1.0/gems/activerecord-4.1.1/lib/active_record/migration.rb:785:in `migrate'
/home/git/gitlab/vendor/bundle/ruby/2.1.0/gems/activerecord-4.1.1/lib/active_record/railties/databases.rake:34:in `block (2 levels) in <top (required)>'
/home/git/gitlab/vendor/bundle/ruby/2.1.0/gems/rake-10.3.2/lib/rake/task.rb:240:in `call'
/home/git/gitlab/vendor/bundle/ruby/2.1.0/gems/rake-10.3.2/lib/rake/task.rb:240:in `block in execute'
/home/git/gitlab/vendor/bundle/ruby/2.1.0/gems/rake-10.3.2/lib/rake/task.rb:235:in `each'
/home/git/gitlab/vendor/bundle/ruby/2.1.0/gems/rake-10.3.2/lib/rake/task.rb:235:in `execute'
/home/git/gitlab/vendor/bundle/ruby/2.1.0/gems/rake-10.3.2/lib/rake/task.rb:179:in `block in invoke_with_call_chain'
/usr/local/lib/ruby/2.1.0/monitor.rb:211:in `mon_synchronize'
/home/git/gitlab/vendor/bundle/ruby/2.1.0/gems/rake-10.3.2/lib/rake/task.rb:172:in `invoke_with_call_chain'
/home/git/gitlab/vendor/bundle/ruby/2.1.0/gems/rake-10.3.2/lib/rake/task.rb:165:in `invoke'
/home/git/gitlab/vendor/bundle/ruby/2.1.0/gems/rake-10.3.2/lib/rake/application.rb:150:in `invoke_task'
/home/git/gitlab/vendor/bundle/ruby/2.1.0/gems/rake-10.3.2/lib/rake/application.rb:106:in `block (2 levels) in top_level'
/home/git/gitlab/vendor/bundle/ruby/2.1.0/gems/rake-10.3.2/lib/rake/application.rb:106:in `each'
/home/git/gitlab/vendor/bundle/ruby/2.1.0/gems/rake-10.3.2/lib/rake/application.rb:106:in `block in top_level'
/home/git/gitlab/vendor/bundle/ruby/2.1.0/gems/rake-10.3.2/lib/rake/application.rb:115:in `run_with_threads'
/home/git/gitlab/vendor/bundle/ruby/2.1.0/gems/rake-10.3.2/lib/rake/application.rb:100:in `top_level'
/home/git/gitlab/vendor/bundle/ruby/2.1.0/gems/rake-10.3.2/lib/rake/application.rb:78:in `block in run'
/home/git/gitlab/vendor/bundle/ruby/2.1.0/gems/rake-10.3.2/lib/rake/application.rb:176:in `standard_exception_handling'
/home/git/gitlab/vendor/bundle/ruby/2.1.0/gems/rake-10.3.2/lib/rake/application.rb:75:in `run'
/home/git/gitlab/vendor/bundle/ruby/2.1.0/gems/rake-10.3.2/bin/rake:33:in `<top (required)>'
/home/git/gitlab/vendor/bundle/ruby/2.1.0/bin/rake:23:in `load'
/home/git/gitlab/vendor/bundle/ruby/2.1.0/bin/rake:23:in `<main>'
Mysql2::Error: Duplicate entry 'ldap' for key 'index_users_on_extern_uid_and_provider'
/home/git/gitlab/vendor/bundle/ruby/2.1.0/gems/activerecord-4.1.1/lib/active_record/connection_adapters/abstract_mysql_adapter.rb:301:in `query'
/home/git/gitlab/vendor/bundle/ruby/2.1.0/gems/activerecord-4.1.1/lib/active_record/connection_adapters/abstract_mysql_adapter.rb:301:in `block in execute'
/home/git/gitlab/vendor/bundle/ruby/2.1.0/gems/activerecord-4.1.1/lib/active_record/connection_adapters/abstract_adapter.rb:373:in `block in log'
/home/git/gitlab/vendor/bundle/ruby/2.1.0/gems/activesupport-4.1.1/lib/active_support/notifications/instrumenter.rb:20:in `instrument'
/home/git/gitlab/vendor/bundle/ruby/2.1.0/gems/activerecord-4.1.1/lib/active_record/connection_adapters/abstract_adapter.rb:367:in `log'
/home/git/gitlab/vendor/bundle/ruby/2.1.0/gems/activerecord-4.1.1/lib/active_record/connection_adapters/abstract_mysql_adapter.rb:301:in `execute'
/home/git/gitlab/vendor/bundle/ruby/2.1.0/gems/activerecord-4.1.1/lib/active_record/connection_adapters/mysql2_adapter.rb:228:in `execute'
/home/git/gitlab/vendor/bundle/ruby/2.1.0/gems/activerecord-4.1.1/lib/active_record/connection_adapters/abstract/schema_statements.rb:397:in `remove_column'
/home/git/gitlab/vendor/bundle/ruby/2.1.0/gems/activerecord-4.1.1/lib/active_record/migration.rb:649:in `block in method_missing'
/home/git/gitlab/vendor/bundle/ruby/2.1.0/gems/activerecord-4.1.1/lib/active_record/migration.rb:621:in `block in say_with_time'
/usr/local/lib/ruby/2.1.0/benchmark.rb:279:in `measure'
/home/git/gitlab/vendor/bundle/ruby/2.1.0/gems/activerecord-4.1.1/lib/active_record/migration.rb:621:in `say_with_time'
/home/git/gitlab/vendor/bundle/ruby/2.1.0/gems/activerecord-4.1.1/lib/active_record/migration.rb:641:in `method_missing'
/home/git/gitlab/db/migrate/20141121161704_add_identity_table.rb:17:in `up'
/home/git/gitlab/vendor/bundle/ruby/2.1.0/gems/activerecord-4.1.1/lib/active_record/migration.rb:598:in `exec_migration'
/home/git/gitlab/vendor/bundle/ruby/2.1.0/gems/activerecord-4.1.1/lib/active_record/migration.rb:579:in `block (2 levels) in migrate'
/usr/local/lib/ruby/2.1.0/benchmark.rb:279:in `measure'
/home/git/gitlab/vendor/bundle/ruby/2.1.0/gems/activerecord-4.1.1/lib/active_record/migration.rb:578:in `block in migrate'
/home/git/gitlab/vendor/bundle/ruby/2.1.0/gems/activerecord-4.1.1/lib/active_record/connection_adapters/abstract/connection_pool.rb:294:in `with_connection'
/home/git/gitlab/vendor/bundle/ruby/2.1.0/gems/activerecord-4.1.1/lib/active_record/migration.rb:577:in `migrate'
/home/git/gitlab/vendor/bundle/ruby/2.1.0/gems/activerecord-4.1.1/lib/active_record/migration.rb:752:in `migrate'
/home/git/gitlab/vendor/bundle/ruby/2.1.0/gems/activerecord-4.1.1/lib/active_record/migration.rb:992:in `block in execute_migration_in_transaction'
/home/git/gitlab/vendor/bundle/ruby/2.1.0/gems/activerecord-4.1.1/lib/active_record/migration.rb:1040:in `ddl_transaction'
/home/git/gitlab/vendor/bundle/ruby/2.1.0/gems/activerecord-4.1.1/lib/active_record/migration.rb:991:in `execute_migration_in_transaction'
/home/git/gitlab/vendor/bundle/ruby/2.1.0/gems/activerecord-4.1.1/lib/active_record/migration.rb:953:in `block in migrate'
/home/git/gitlab/vendor/bundle/ruby/2.1.0/gems/activerecord-4.1.1/lib/active_record/migration.rb:949:in `each'
/home/git/gitlab/vendor/bundle/ruby/2.1.0/gems/activerecord-4.1.1/lib/active_record/migration.rb:949:in `migrate'
/home/git/gitlab/vendor/bundle/ruby/2.1.0/gems/activerecord-4.1.1/lib/active_record/migration.rb:807:in `up'
/home/git/gitlab/vendor/bundle/ruby/2.1.0/gems/activerecord-4.1.1/lib/active_record/migration.rb:785:in `migrate'
/home/git/gitlab/vendor/bundle/ruby/2.1.0/gems/activerecord-4.1.1/lib/active_record/railties/databases.rake:34:in `block (2 levels) in <top (required)>'
/home/git/gitlab/vendor/bundle/ruby/2.1.0/gems/rake-10.3.2/lib/rake/task.rb:240:in `call'
/home/git/gitlab/vendor/bundle/ruby/2.1.0/gems/rake-10.3.2/lib/rake/task.rb:240:in `block in execute'
/home/git/gitlab/vendor/bundle/ruby/2.1.0/gems/rake-10.3.2/lib/rake/task.rb:235:in `each'
/home/git/gitlab/vendor/bundle/ruby/2.1.0/gems/rake-10.3.2/lib/rake/task.rb:235:in `execute'
/home/git/gitlab/vendor/bundle/ruby/2.1.0/gems/rake-10.3.2/lib/rake/task.rb:179:in `block in invoke_with_call_chain'
/usr/local/lib/ruby/2.1.0/monitor.rb:211:in `mon_synchronize'
/home/git/gitlab/vendor/bundle/ruby/2.1.0/gems/rake-10.3.2/lib/rake/task.rb:172:in `invoke_with_call_chain'
/home/git/gitlab/vendor/bundle/ruby/2.1.0/gems/rake-10.3.2/lib/rake/task.rb:165:in `invoke'
/home/git/gitlab/vendor/bundle/ruby/2.1.0/gems/rake-10.3.2/lib/rake/application.rb:150:in `invoke_task'
/home/git/gitlab/vendor/bundle/ruby/2.1.0/gems/rake-10.3.2/lib/rake/application.rb:106:in `block (2 levels) in top_level'
/home/git/gitlab/vendor/bundle/ruby/2.1.0/gems/rake-10.3.2/lib/rake/application.rb:106:in `each'
/home/git/gitlab/vendor/bundle/ruby/2.1.0/gems/rake-10.3.2/lib/rake/application.rb:106:in `block in top_level'
/home/git/gitlab/vendor/bundle/ruby/2.1.0/gems/rake-10.3.2/lib/rake/application.rb:115:in `run_with_threads'
/home/git/gitlab/vendor/bundle/ruby/2.1.0/gems/rake-10.3.2/lib/rake/application.rb:100:in `top_level'
/home/git/gitlab/vendor/bundle/ruby/2.1.0/gems/rake-10.3.2/lib/rake/application.rb:78:in `block in run'
/home/git/gitlab/vendor/bundle/ruby/2.1.0/gems/rake-10.3.2/lib/rake/application.rb:176:in `standard_exception_handling'
/home/git/gitlab/vendor/bundle/ruby/2.1.0/gems/rake-10.3.2/lib/rake/application.rb:75:in `run'
/home/git/gitlab/vendor/bundle/ruby/2.1.0/gems/rake-10.3.2/bin/rake:33:in `<top (required)>'
/home/git/gitlab/vendor/bundle/ruby/2.1.0/bin/rake:23:in `load'
/home/git/gitlab/vendor/bundle/ruby/2.1.0/bin/rake:23:in `<main>'
Tasks: TOP => db:migrate

Please help me!

Thanks!