[devtools/qunit] Retain firefox process stdout to eventually print it
The bare RuntimeError that gets emitted upon timeout does not help much to
diagnose the problem. Let's see if we can get more information from stdout by
not dropping it.
addressbook
basket
blog
book
calendar
comment
company
email
file
folder
i18ncontent
keyword
link
mailinglist
person
tag
timeseries
vcsfile