[web/calendar] fix regression in previous changeset "Enables css customization in CalendarView" was untested, and introduced a crash: TypeError: not all arguments converted during string formatting

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