ssl_certificate is not important for http only checks.

"Extended" status codes, like 524, 526 and others, come from surykatka
itself and shall be amended with additional explanation

Since standard date format is used in the ssl_certificate checks, do the
same for readability and consistency in bot_status.

/reviewed-on nexedi/slapos.toolbox!72

/reviewed-on nexedi/slapos.toolbox!68

There was mistake, as result_max[0] is already free disk space, so there
was no need to do 1. - result_max[0]. Unfortunately tests were also
incorrectly adjusted.

In case of error the drop of free space percentage is shown.

The most important information is if the disk won't become full in some time,
by default 30 days. This check uses collector db history to calculate speed
of filling the disk and predicts when it will become full.

Instead of outdated approach with threshold-file just support threshold,
provided in float in GB, defaulting to 5% of disk size if found in the
database and fallback to 2.0 GB, to raise promise error.

/reviewed-on nexedi/slapos.toolbox!63

/reviewed-on nexedi/slapos.toolbox!51

/reviewed-on nexedi/slapos.toolbox!59

promise-timeout provides global timeout for the promise, so use it as
base for calculating default timeout.

/reviewed-on nexedi/slapos.toolbox!58

Enhancements:

 * implement ignore-code
 * cover http_code
 * cover timeout
 * implement verify
 * correctly cover ca-cert-file
 * use SLAPOS_TEST_IPV4

Improvements:

 * flake8ize test_check_url_available and check_url_available
 * cover more of check_url_available

It will be easier to improve it soon.

/reviewed-on nexedi/slapos.toolbox!53

This promises are used in caddy-frontend to check slave frontend status. We don't want to run them everytime buildout will deploy frontend because:
- there is too many slaves, check all slave frontend promises while deploying frontend will slow down slave frontend deployment.
- we don't want to reprocess frontend if one of slave frontend promise is failing

First start of promise migration to new python promises format. Promises migrated here are
used in caddy-frontend and monitor stack.

The promise should not fail if the backup was never launched because the instance just deployed.

/reviewed-on nexedi/slapos.toolbox!47

This is the promise that will be used for the backupserver software release. It is working as is (with some needed changes in backupserver software release of course) but I may add more features.

I'd like to have a first review of my code.

/reviewed-on nexedi/slapos.toolbox!43

This promise will replace the old check_port_listening promise (https://lab.nexedi.com/nexedi/slapos/blob/master/slapos/recipe/check_port_listening.py). See https://www.erp5.com/slapos-TechnicalNote.General.SlapOS.Monitoring.Specifications for how to instantiate this promise in buildout.

/reviewed-on nexedi/slapos.toolbox!42

This solve indefinite loop in while condition on promise check_free_disk_space