Since 2de4c80f generic_mysql does not
sleep so long between retries

This recipe now uses strings for ip

See merge request !741

See merge request !720

See merge request !739

TODO: There are still direct references to specific version of Python in:
  - slapos component
  - bazel templates
  - nextcloud & theia SR

if last_backup was an int, the script failed with this error:

result undefined, global datetime = <module 'datetime' from '/srv/slapgrid/
slappart6...6d33cee74/lib/python2.7/lib-dynload/datetime.so'>,
datetime.datetime = <type 'datetime.datetime'>,
datetime.datetime.fromtimestamp = <built-in method fromtimestamp of type
object>, last_backup = '1587724103'
<type 'exceptions.TypeError'>: a float is required
      args = ('a float is required',)
      message = 'a float is required'

This was broken in 8725ab1a.

fix the way of getting parameters in the new recipe.

 * fix section pbs in instance-pull-backup.cfg.in after change of
argument names.
 * fix the order of the 2 callbacks as the order is very important

See nexedi/slapos!739

Also use better argument names. The function is used in pbs recipe and
was wrongly removed in 569439d5 commit.

See nexedi/slapos!739

The '.lock' suffix is automatically added by lockfile. See
https://opendev.org/openstack/pylockfile/src/tag/0.12.2/lockfile/__init__.py#L218

See nexedi/slapos!739

extra_requires was added in slapos.core, which simplifies this part.

It is broken since commit 71ed0078
("pdftk removed from erp5").

For repositories with patches, the latter should be downloaded first.

Another issue that remains unfixed is that during the build of some
components, some data are cached in ~/.cache and this can break further
builds with the same user.

Former URL of models is now 404. Thus use proper offcial github location (no change of md5sum of file).

As we can see in the testcases added, since we started to use Firefox 60, fonts were no longer selected and some garbage characters were displayed instead of the text.

Before these changes, it looked like this:

![screenshot_test.TestFirefox60.test_screenshot_before](/uploads/7ffe2eb7678b9f62ae13a56f4c8b57cf/screenshot_test.TestFirefox60.test_screenshot_before.png)

now it looks like this:

![screenshot_test.TestFirefox60.test_screenshot_after](/uploads/6d178ebdac388e534206149e97de08a1/screenshot_test.TestFirefox60.test_screenshot_after.png)

which is of course better, but still wrong, because the test case uses Arial and this font is not Arial. This part will be fixed later.

It seems firefox no longer accepts fonts from slapos directories, before the fix, firefox prints this on console:
    
    (./parts/firefox-60/firefox:7277): Pango-WARNING **: 08:06:33.942: failed to create cairo scaled font, expect ugly output. the offending font is 'IPAGothic 9.9990234375'
    (./parts/firefox-60/firefox:7277): Pango-WARNING **: 08:06:33.942: font_face status is: file not found
    (./parts/firefox-60/firefox:7277): Pango-WARNING **: 08:06:33.942: scaled_font status is: file not found
    (./parts/firefox-60/firefox:7277): Pango-WARNING **: 08:06:33.942: shaping failure, expect ugly output. shape-engine='PangoFcShapeEngine', font='IPAGothic 9.9990234375', text='?'
    (./parts/firefox-60/firefox:7277): Pango-WARNING **: 08:06:33.943: failed to create cairo scaled font, expect ugly output. the offending font is 'IPAGothic 9.9990234375'
    (./parts/firefox-60/firefox:7277): Pango-WARNING **: 08:06:33.943: font_face status is: file not found
    (./parts/firefox-60/firefox:7277): Pango-WARNING **: 08:06:33.943: scaled_font status is: file not found

but the file exists... Maybe this is a bug in firefox ( https://bugzilla.mozilla.org/show_bug.cgi?id=1336049#c2 looks similar, even though for us in firefox 52 it was fine and the problem appeared between 52 and 60).

A simple workaround is to copy all fonts in firefox fonts' directory.

See merge request !736

${xvfb-instance:display} is used in in runTestSuite.in

"bin/pythonwitheggs" no longer exist

See merge request !738

"bin/pythonwitheggs" no longer exist

See merge request !737