Commit cf853a78 removed all yml tests
and the yml import engine from Odoo forever, however PyYAML remains a
dependency even though it's not used anymore.

This commit removes any reference to this lib that could be found.

closes odoo/odoo#27563

A dependency to libsass was added in debian package and in the docker
file. The Odoo nightly builds of the deb package was failing because
this lib is named libsass0 in Debian.

Finally, this dependency is not required because python3-libsass already depends on libsass0.

Include libsass instead of node-less

Thank you to @d-fence for testing this.

The automated tests of rpm,deb and src packages are using docker
images and containers. Those tests were not working as expected due
to various small glitches:
* some debian python- packages were missing in the Debian image
* pip was called instead of pip3 for the src test
* a wrong addons path was given for the tests
* the containers id's were wrong due to a bytes implicitly converted
  to str

Purpose: openid is not used anymore in Odoo, therefore it can be
safely removed.

Complements 021de21e and #16918

Before this patch, the debian package depends on `python-pybabel`.
According to the documentation, this is a dummy package for transition
from `python-pybabel` to `python-babel`[1].

This dummy package has thus been removed in debian stretch in favor of
`python-babel`, and the odoo package is thus not installable in debian
stretch.

To fix this, we depend directly on `python-babel`, which is available in
all debian releases[2].

Closes #13905

[1] https://packages.debian.org/jessie/python-pybabel
[2] https://packages.debian.org/jessie/python-babel

* Remove dependency on less-plugin-clean-css which distribution
  packages are broken on debian stretch and derivated.
* Updated documentation.
* Lessc provides a `--compress` argument that could solve this issue.
  According to the documentation at http://lesscss.org/usage/: "[...]
  Compress using less built-in compression. This does an okay job but
  does not utilise all the tricks of dedicated css compression[...]"
  However, using this argument works on lessc 2.5.3 but not on 1.4.2
  (`--compress` arg is present but seems to be break some rules
  i haven't been able to put my finger on).
* Finally, use the minification of the StylesheetAsset that takes care
  of removing the spaces, the comments and the sourcemap with regexes.

fixes issue #9113

because it's available in debian stable but not in ubuntu 14.04 (lts)

The stdlib version of the json library is more recent than the 3.5.3
version we are pinning in `requirements.txt`

There is no reason to use it.

Closes #6940

The `unittest2` package is simply a backport of `unittest` from the
Standard Library of Python 2.7 to previous versions.

There is no reason to use it any longer.

Closes #6941

It was preventing postgresql to generate a working cluster.

It was preventing postgresql to generate a working cluster.

It was preventing postgresql to generate a working cluster.

Update to pip v6 necessary to avoid import error of 'IncompleteRead' from requests.compat

Creation of a Dockerfile for the src package for nightly tests.
Remove unnecessary libraries installation from the Debian Dockerfile.

RPM packages did not pass the tests because the centos prompt changed
and thus did not match the regexp anymore. We now explicitely specify
the prompt in our Dockerfiles to prevent such issues.

RPM packages did not pass the tests because the centos prompt changed
and thus did not match the regexp anymore. We now explicitely specify
the prompt in our Dockerfiles to prevent such issues.

Remove installation of v8 requirements in package.dfdebian as this
is unnecessary for v7. This fixes a bug occuring during the installation
of openerp (precisely when installing reportlab dependencies), because
reportlab now requires a more recent version of pillow than 2.5.1.
Also use pip instead of /usr/local/bin/pip in test_tgz (package.py)
as pip script isn't installed there anymore.

[REF] Packaging: backport of a7ab5a41
[REF] Packaging: backport of a700a113
[REF] Packaging: backport of 9d0bd280
[REF] Packaging: backport of b0722d3e
[REF] Packaging: backport of 24b2c938
[REF] Packaging: backport of e874cdaf
[REF] Packaging: backport of 56b61da1
[REF] Packaging: backport of be96dd85
[REF] Packaging: backport of 50a4da99
[REF] Packaging: backport of 1c41f369
[REF] Packaging: backport of cc113317
[FIX] Packaging: backport of 13471630
[REF] Package: backport of 93845d68
[REF] Package: backport of 012bc01c
[FIX] Package: partial apply of d9e72a37
[REF] Package: backport of 67036fef
[REF] Package: backport of 73de0138
[REF] Package: backport of 30d987ed
[REF] Package: backport of 29132669
[REF] Package: backport of 7db12dc4
[REF] Package: backport of f668f9c6
[REF] Package: backport of 2cf4051a
[REF] Packaging: backport of 73592487
[REF] Packaging: backport of f2598ecd
[REF] Package: backport of fd21912c
[REF] Package: backport of 9a8cdf49
[REF] Package: backport of 2f4984b8
[REF] Package: backport of 6e9edeeb
[REF] Package: partial backport of d4624fa8
[REF] Package: backport of 9f13722f

This way we'll be using docker cache to spare dependencies download time.