class ActiveRecord::TransactionRollbackError

dev.mysql.com/doc/mysql-errors/en/server-error-reference.html#error_er_lock_deadlock<br>* www.postgresql.org/docs/current/static/transaction-iso.html<br><br>See the following:
back by the database due to a serialization failure or a deadlock.
TransactionRollbackError will be raised when a transaction is rolled