[DRE-maint] Redmine in buster

[Marc Dequènes (duck)]

Coin,

It seems autopkgtest has various bugs affecting run with LXC and Salsa 
too. #766063 matches my problem but I've stopped using libpam-tmpdir 
because it broke various things so it's strange.

Anyway I decided to stop losing my time and take advantage of the 
recently advertized CI pipeline of Salsa. Utkarsh Gupta already kindly 
enabled it so I could have a look at the results.
Except for autopkgtest blocked by #934789 at least, I disabled the 
migration tests for piuparts temporarily and all is green.

As the dependency problem is a real annoyance and even if it's not as 
well tested as I would like I decided to upload the current work (seems 
my upload is lagging behind though). Feedback welcome.

\_o<

-- 
Marc Dequènes