Make test database cache lookup concurrent has_cache() is used to dertermine if the template database already exists or not. When running tests accross multiple process, has_cache() wasn't aware of databases created by other processes because it used a cache to generate the cache... Since the discovering discover_cached_db() time is quite reasonable (it's just about listing file in a directory), let re-generate the cache on cache miss.

etc/init.d
etc/cubicweb.d
etc/bash_completion.d
usr/bin
usr/share/doc/cubicweb-ctl
var/log/cubicweb
var/lib/cubicweb/backup
var/lib/cubicweb/instances