ActiveRecord can't insert schema_migrations version due to dropped connection

[steverice]

At the end of a long-running pt-osc migration, this error can occur:

rake aborted!
StandardError: An error has occurred, all later migrations canceled:

Mysql2::Error: MySQL server has gone away: INSERT INTO `schema_migrations` (`version`) VALUES ('20150622154913') 

ActiveRecord's MySQL connection is likely exceeding the server's wait_timeout and hence its connection gets dropped.
The likely fix is to refresh/re-establish the MySQL connection after pt-osc completes and before inserting the version.

[steverice]

Fixed by #17.