coreutils
imagemagick
poppler

If there is no binlog in srv/backup/mariadb-incremental (ie : the parameter
incremental_backup_retention_days is set to -1), then the import script fails.
This should not happen as this script just updates some inline paths.
This commit just add a correct check on variables and files existence

Each loop in jinja2 has its own scope. This code was likely relying on a
bug, which was probably recently fixed upstream.
Using generators is cleaner as it better expresses the intent.

Jupyter: Add extra_data_list option to support display data similar to the original jupyter python backend.

slapos.cookbook:generic.zope.zeo.client did not let buildout know about
site.zcml file it creates. So it would not be deleted on update, making
slapos.cookbook:symbolic.link fail as it carefully avoids deleting
non-links.
So, copy site.zcml instead of sym-linking.

Such complex recipes prevent evolution. Split it into individual
components already covered by existing recipes.

/reviewed-on !117

resilient: adds a promise to test integrity and the status of the last run of the feeds generated by notifier scripts

because zope.interface is not required to build rebootstrap python.

This commit is a fix for 8787716d. It allows to get the random cron string
generated previously through parameters, and not reading manually .installed.cfg.