Mixins not already imported were not available in Portal Type UI (#20140326-1A7D11).

Instead of inspecting the content of mixin modules, which relies on already
imported module, use the same approach as Document (updateGlobals()), eg using
FS path so that even modules not already beforehand are not ignored.

product/ERP5/__init__.py

@@ -88,10 +88,6 @@ portal_tools = ( CategoryTool.CategoryTool,
 content_classes = ()
 content_constructors = ()
 
-
-# XXX-AUREL : see bug #20140326-1A7D11
-from mixin import periodicity
-
 # Finish installation
 def initialize( context ):
   import Document

product/ERP5Type/Utils.py

@@ -1111,11 +1111,14 @@ def initializeProduct( context,
   mixin_module = getattr(this_module, 'mixin', None)
   if mixin_module is not None:
     from Products.ERP5Type import mixin_class_registry
-    for k, submodule in inspect.getmembers(mixin_module, inspect.ismodule):
+    import importlib
+    path, module_id_list = getModuleIdList(package_home(this_module.__dict__), 'mixin')
+    for module_id in module_id_list:
+      submodule = importlib.import_module('%s.%s' % (mixin_module.__name__, module_id))
       for klassname, klass in inspect.getmembers(submodule, inspect.isclass):
         # only classes defined here
         if 'mixin' in klass.__module__ and not issubclass(klass, Exception):
-          classpath = '.'.join((module_name, 'mixin', k, klassname))
+          classpath = '.'.join((module_name, 'mixin', module_id, klassname))
           mixin_class_registry[klassname] = classpath
 
   product_name = module_name.split('.')[-1]