Setting mysql.implementation to AphrontMySQLDatabaseConnection results in an exception, even though it works with AphrontMySQLiDatabaseConnection.
I did this in the shell:
$ bin/config set mysql.implementation AphrontMySQLiDatabaseConnection Set 'mysql.implementation' in local configuration. $ bin/config set mysql.implementation AphrontMySQLDatabaseConnection Usage Exception: Option 'mysql.implementation' value must name a class extending 'AphrontMySQLDatabaseConnectionBase'.
Version: f75b1cf562c0c3646324864851d693ef1069a068 which is the stable branch from 2016-04-18