Work around trytond.module not being a real namespace module.

Solution is to add all trytond module's locations to
trytond.modules._path__. This will make trytond.module behave much
like a namespace module.
Adding to __path__ is done in update_egg_modules() to ensure __path__
is updated whenever the list of egg modules is updated.

*** a/trytond/modules/__init__.py	1970-01-01 01:00:01.000000000 +0100
--- b/trytond/modules/__init__.py	2021-12-02 18:12:15.385101986 +0100
***************
*** 38,43 ****
--- 38,46 ----
          import pkg_resources
          for ep in pkg_resources.iter_entry_points('trytond.modules'):
              EGG_MODULES[ep.name] = ep
+             path = os.path.join(ep.dist.location, 'trytond', 'modules')
+             if not path in __path__ and os.path.isdir(path):
+                 __path__.append(path)
      except ImportError:
          pass
  
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<div class='path'>path: <a href='/guix/log/?id=952963aba8db1a052fd86920d95be16ad56de187'>root</a>/<a href='/guix/log/tests?id=952963aba8db1a052fd86920d95be16ad56de187'>tests</a>/<a href='/guix/log/tests/guix-locate.sh?id=952963aba8db1a052fd86920d95be16ad56de187'>guix-locate.sh</a></div><div class='content'><table class='list nowrap'><tr class='nohover'><th class='left'>Age</th><th class='left'>Commit message (<a href='/guix/log/tests/guix-locate.sh?id=952963aba8db1a052fd86920d95be16ad56de187&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2023-11-15 18:29:37 +0100'>2023-11-15</span></td><td><a href='/guix/commit/tests/guix-locate.sh?id=69d9a020949c77c77b449c1faf04397b95eef5b7'>locate: Accept ‘--clear’ without additional arguments.</a><span class='msg-avail'>...<span class='msg-tooltip'>Fixes a bug whereby ‘guix locate --clear’ would end with the “no files
to search for” error.

Fixes &lt;https://issues.guix.gnu.org/66799&gt;.

* guix/scripts/locate.scm (guix-locate): Do not emit “no files to search
for” error when 'clear? is set in OPTS.
* tests/guix-locate.sh: Test it.

Reported-by: Maciej Kalandyk &lt;m.kalandyk@outlook.com&gt;
Change-Id: Ib8fa125c18481d7f5408bd89df9503713527641d
</span></span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2023-06-18 23:44:29 +0200'>2023-06-18</span></td><td><a href='/guix/commit/tests/guix-locate.sh?id=1b7aabbc79969a89141aadd3d41d7a5329a3462e'>Add 'guix locate'.</a><span class='msg-avail'>...<span class='msg-tooltip'>* guix/scripts/locate.scm, tests/guix-locate.sh: New files.
* Makefile.am (MODULES): Add 'guix/scripts/locate.scm'.
(SH_TESTS): Add 'tests/guix-locate.sh'.
* po/guix/POTFILES.in: Add it.
* doc/guix.texi (Invoking guix locate): New node.

Co-authored-by: Antoine R. Dumont &lt;antoine.romain.dumont@gmail.com&gt;
</span></span></td><td>Ludovic Courtès</td></tr>