It sometimes happend that buildout unistall/install the section with this recipe,
which remore storage_path file and recreate it. In most of cases this is not wanted
because the recipe is used to generate password, so that password will change when this
happend.
To prevent buildout to remove storage_path, I introduced a new option 'create-once'
which, when set to True (the default value) will not let buildout play with storage_path file
by returning None in install recipe. Also install won't remove the file if the size is not 0.

/reviewed-on !129

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.

Needed by ERP5 software release.

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

The http one was redirecting to it.

/reviewed-by: TrustMe

In case of failure, it gives a change to inspect test data of the first line.

The watcher should also watch for signals like SIGTERM killing sidekiq, which
are trapped by sidekiq, with sidekiq exiting successfully (with exit code 0).

To achieve this we rework our watcher-sigkill to be a generic watcher -
that can be given a set of restart exit codes including signal names and
monitors whether child process terminated with matching for restart exit
code.

Example usage:

	watcher 0,SIGKILL prog ...

Based on patch by @iv.
Discussion: https://lab.nexedi.com/lab.nexedi.com/lab.nexedi.com/issues/25#note_22085

Also allow to change promise timeout by editing check_url_PROMISE_TIMEOUT file

An issue on Gitlab SR when pushing on protected branches occurs with git 2.11.
Gitlab issue: https://gitlab.com/gitlab-org/gitlab-ce/issues/25601

Fixes: https://lab.nexedi.com/lab.nexedi.com/lab.nexedi.com/issues/37

Getting them from the runner backup avoids to get false positive if some
of the instance's backup files were excluded using an exporter.exclude file