only for python3

We now need to install lxml-clean-html separately, see the following
message:

  File "/srv/slapgrid/slappart71/srv/runner/software/e16145ec9280f63bd6c28ca2758d03f0/develop-eggs/lxml-5.2.1-py3.9-linux-x86_64.egg/lxml/html/clean.py", line 18, in <module>
    raise ImportError(
ImportError: lxml.html.clean module is now a separate project lxml_html_clean.

See https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99090

We need to patch ffmpeg to be able to compile with this version of
binutils.

Currently libsnappy is being compiled in the folder lib64 in some
OSes (e.g. SUSE SLE 15.6).
This is a problem because some dependents look for the library in the
lib subdirectory.
This change forces snappy to always use the lib directory.

See merge request nexedi/slapos!1581

This is a follow-up of 7a1ba8df.

because re6stnet only supports OpenVPN 2.4.
This reverts commit 6802867d.

When compiling older GCC versions in newer machines, libsanitizer
does not compile, showing a error: `multiple definition of
'enum fsconfig_command'` (e.g.
https://github.com/llvm/llvm-project/issues/56421).
This is because starting from Glibc 2.36, it is not possible to include
both "linux/fs.h" and "sys/mount.h".

We can apply a patch, similar to the one in
https://reviews.llvm.org/D129471 , but with the extension and lines
changed to match the file. This is also similar to the upstream fix.

See merge request nexedi/slapos!1579

This will be used to add the sqlite3 binary directory to PATH.

See nexedi/neoppod@5923f8f5

This now supports producing html reports directly

nbd2-host and nbd2-port are asserted too.

Test are reorganized to easily assert mixed scenarios.

Zope no longer serve XML-RPC in ERP5, unless it is explicitly enabled
using this.

See nexedi/erp5!1931

--enable-readline is broken:
  - it searches for readline.h instead of readline/readline.h
  - it does not abort when it fails to find headers
Use --with-readline-inc so that it sets HAVE_READLINE.

Also use the dedicated configure option to enable update limit.
And sqlite3 does not depend directly on ncurses.

See nexedi/neoppod@71564067

See merge request nexedi/slapos!1566

See merge request nexedi/slapos!1576

See merge request nexedi/slapos!1572

to avoid the following error:
relocation R_X86_64_32S against `.rodata' can not be used when making a shared object; recompile with -fPIC

software/osie-coupler: keep the build source directory instead of having another open62541-source part.