[DRE-maint] Bug#848288: ruby-em-synchrony: (build-)depends on mysql-{client, server}

[Christian Hofstaedtler]

* Emilio Pozuelo Monfort <pochu at debian.org> [161219 01:22]:
> Your package build-depends on mysql-server. Since we're transitioning to
> mariadb as the default mysql provider, you should switch your build
> dependency to default-mysql-server | virtual-mysql-server.

While I've done so now in the recent upload, I think this is
misguided: the mysql-server implementations are not nearly
compatible enough to allow switching between them.

* mysql_install_db takes different parameters (--force is missing in
  5.7)
* mariadb sets up users with a default plugin of `unix_socket` which
  needs workarounding
* --skip-grant works differently between mysql and mariadb (mariadb
  does not allow SET PASSWORD after FLUSH PRIVILEGES in this mode)
* the default character sets differ, and as such the valid indexes that
  can be created differ.

None of these are just theoretical issues.

-- 
christian hofstaedtler <zeha at debian.org>