ruby-mysql2 binary package in Ubuntu Xenial s390x

 This is an API module that allows Ruby programs to interface with MySQL
 databases. Usually, it will be pulled in automatically by packages providing
 Ruby programs which need this capability, you only need to install it directly
 if you intend to write such programs yourself. You may want to prefer the
 ruby-mysql2 package over the ruby-mysql package, since benchmarks have shown
 it to be faster, it is non-blocking and it supports UTF-8 database encoding.

Source package