[DRE-maint] redmine: fails to install: Please install the mysql adapter

[Jérémy Lal]

When using ruby-mysql2, the adapter name in
/etc/redmine/<instance>/database.yml
must be 'mysql2'.
The only way to fix this is to ask the user which
adapter he intends to use...

If ruby-mysql2 can replace ruby-mysql, why not
provide the same adapter name and make those packages not
co-installable ?

Jérémy.