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
  
tr>
<tr><td class='sub'>Wojtek's customized Guix</td><td class='sub right'></td></tr></table>
<table class='tabs'><tr><td>
<a href='/guix/about/'>about</a><a href='/guix/'>summary</a><a href='/guix/refs/?id=06f47e0256c45aca3b65efb9718b14f9ee669709'>refs</a><a class='active' href='/guix/log/gnu/services/rsync.scm'>log</a><a href='/guix/tree/gnu/services/rsync.scm?id=06f47e0256c45aca3b65efb9718b14f9ee669709'>tree</a><a href='/guix/commit/gnu/services/rsync.scm?id=06f47e0256c45aca3b65efb9718b14f9ee669709'>commit</a><a href='/guix/diff/gnu/services/rsync.scm?id=06f47e0256c45aca3b65efb9718b14f9ee669709'>diff</a></td><td class='form'><form class='right' method='get' action='/guix/log/gnu/services/rsync.scm'>
<input type='hidden' name='id' value='06f47e0256c45aca3b65efb9718b14f9ee669709'/><select name='qt'>
<option value='grep'>log msg</option>
<option value='author'>author</option>
<option value='committer'>committer</option>
<option value='range'>range</option>
</select>
<input class='txt' type='search' size='10' name='q' value=''/>
<input type='submit' value='search'/>
</form>
</td></tr></table>
<div class='path'>path: <a href='/guix/log/?id=06f47e0256c45aca3b65efb9718b14f9ee669709'>root</a>/<a href='/guix/log/gnu?id=06f47e0256c45aca3b65efb9718b14f9ee669709'>gnu</a>/<a href='/guix/log/gnu/services?id=06f47e0256c45aca3b65efb9718b14f9ee669709'>services</a>/<a href='/guix/log/gnu/services/rsync.scm?id=06f47e0256c45aca3b65efb9718b14f9ee669709'>rsync.scm</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/gnu/services/rsync.scm?id=06f47e0256c45aca3b65efb9718b14f9ee669709&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2019-03-04 15:22:58 +0100'>2019-03-04</span></td><td><a href='/guix/commit/gnu/services/rsync.scm?id=56a93cb975ddc33d50183fb122e2aafda026f18e'>services: Use 'file-append' for user account shells.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/services/cuirass.scm (cuirass-account): Use 'file-append' instead
of #~(string-append #$shadow "/sbin/nologin").
* gnu/services/monitoring.scm (zabbix-server-account): Likewise.
(zabbix-agent-account): Likewise.
* gnu/services/rsync.scm (rsync-account): Likewise.
* gnu/services/ssh.scm (%openssh-accounts): Likewise.
</span></span></td><td>Ludovic Courtès</td></tr>