[datafeed] also catch EnvironmentError when trying to load the cwclientlib config file means the config file has not been found, so fall back to the old implementation instead of crashing.

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