Done through various 2to3 fixers (zope.fixers, modernize, future) and manual
changes. This is a single commit so that we have a clearer picture of how code
converted with my2to3 should look like.

Except straightforward @implementer decorator 2to3 fixer, only product/ folder
was considered as the goal was to be able to create an ERP5Site.

* Use @implementer decorator introduced in zope.interface 3.6.0 (2010):

  The implements syntax used under Python 2.X does not work under 3.X, since it
  depends on how metaclasses are implemented and this has changed. Instead it
  now supports a decorator syntax (also under Python 2.X).

  Applied thanks to 2to3 `zope.fixers` package.

* Use `six.moves` rather than `future` install_aliases() feature because the
  latter use unicode_literals and "wraps" module aliases so that unicode() are
  returned for text rather than str() (Python2 standard library). This notably
  breaks BusinessTemplate code which uses urllib quote() for filesystem paths...

* No more unbound methods in python3 so use six.get_unbound_function().

* dict.(iteritems,iterkeys,itervalues)() => six.\1(dict) thanks to `dict_six`
  2to3 fixer from `modernize`:
  $ python-modernize -w -f dict_six product/

* Manually make sure that dict.{items,values,keys}() returns a real list when it
  is latter modified rather than a dict_{items,values,keys} (ensure_list()). By
  default, 2to3 blindly does list(dict.{items,values,keys}()) which is not
  acceptable from performances point of view. With my2to3, this will be possible
  to handle such case automatically.

* Replace cStringIO.StringIO() by six.moves.cStringIO() (a module alias for
  cStringIO.StringIO() on py2 and io.StringIO() on py3).

* Use six.text_type which maps to unicode() on py2 and str() on py3. This also
  makes a clearer difference between text and binary strings.

* Replace map()/filter() with lambda function by list comprehension (this has
  the benefit to avoid casting to list for py3 as it returns iterators).

* past.builtins:
  portal_skins/erp5_core/Base_sortObjectListLikeSQL:0:2:Redefining built-in 'cmp' (redefined-builtin)
* six and six.moves imports:
  + portal_skins/erp5_core/Base_updateListboxSelection:0:2:Redefining built-in 'basestring' (redefined-builtin)
  + portal_skins/erp5_core/ERP5Site_checkDataWithScript:20:2:Redefining built-in 'xrange' (redefined-builtin),

Use the latter form that works on both. On non-PythonScript code, this is of
course not an issue but Python2 PythonScript does not have a __code__ properties
and requires a patch on Shared.DC.Scripts.Signature (applied by SlapOS recipe)
so that FuncCode() object is set to not only func_code but also __code__.

And also disable pylint patch as pylint version with Python3 support is not
supported yet by ERP5...

* Add functions to properly convert/handle bytes/str/unicode (from
  slapos.util) (stricter than six.ensure_{text,str}()).
* Python3 {keys,values,items}() now returns dict_{keys,values,items} rather than
  real list() so add ensure_list() to create a list() when it is latter modified
  but do nothing on Python2 for performance sake.

  File "product/TimerService/timerserver/TimerServer.py", line 71, in run
    s.send('GET / HTTP/1.1\r\n\r\n')
TypeError: a bytes-like object is required, not 'str'

And Zope4 now mandates it to be a string ({Shared.DC.ZRDB.TM.TM,ITransactionManager}.sortKey()).

This changes the API to implement similar feature in Python3, but this should
not be an issue because Interactor are only for non-ERP5 object...

py3: AccessControl users_with_local_roles() returns a dict_keys() instead of a subscriptable object.

Submitted upstream:
  https://github.com/zopefoundation/AccessControl/pull/128

py3: DCWorkflow is python2-only so make ERP5Site creation work on Python3 WITH_LEGACY_WORKFLOW=False.

ERP5 Workflow implementation should ideally not depend on DCWorkflow at all so
that legacy DCWorkflow can be disabled for Python2 but this would require much
more work.

Mainly for maintenance sake and to update the code before porting it to python3.

See merge request nexedi/erp5!1614

Seems required for Chameleon 3.2

See also commit 8c222bd5
("Switch to class-based completely instead of id-based styling").

See merge request nexedi/erp5!1611

we may get stopped SM in some case, maybe it's because sql is not updated.

here is some trackback:
------
2022-05-02 09:30:17,457 INFO InvoiceTransaction_selectInvoiceMovement, 37: <object object at 0x7f707a6e61f0> started  sm
------
2022-05-02 09:30:17,459 INFO InvoiceTransaction_selectInvoiceMovement, 37: <object object at 0x7f707a6e61f0> started  sm
------
2022-05-02 09:30:17,579 INFO InvoiceTransaction_selectDelivery, 27: <object object at 0x7f707a6e61f0> {<Sale Invoice Transaction at /nexedi/accounting_module/20220502-3DD4B45>: 1}
==> slappart8/var/log/zope-0-event.log <==               ***************************** deliver sale invoice transaction
------
2022-05-02 09:30:21,512 INFO RuleTool Updating simulation for /nexedi/accounting_module/20220502-3DD4B45: {'create_root': 1, 'index_related': 1}

==> slappart5/var/log/zope-0-event.log <==
------
2022-05-02 09:30:22,892 WARNING SQLDict Exception raised when invoking messages (uid, path, method_id) [(275788776658006010L, ('', 'nexedi', 'accounting_module', '20220502-3DD4B45'),
'_localBuild')]
Traceback (most recent call last):
  File "/srv/slapgrid/slappart16/srv/runner/software/cc627918c55102e3f1a6c6a0077f41bb/parts/erp5/product/CMFActivity/Activity/SQLBase.py", line 868, in dequeueMessage
    transaction.commit()
  File "/srv/slapgrid/slappart16/srv/runner/software/cc627918c55102e3f1a6c6a0077f41bb/eggs/transaction-1.7.0-py2.7.egg/transaction/_manager.py", line 123, in commit
    return self.get().commit()
  File "/srv/slapgrid/slappart16/srv/runner/software/cc627918c55102e3f1a6c6a0077f41bb/eggs/transaction-1.7.0-py2.7.egg/transaction/_transaction.py", line 280, in commit
    reraise(t, v, tb)
  File "/srv/slapgrid/slappart16/srv/runner/software/cc627918c55102e3f1a6c6a0077f41bb/eggs/transaction-1.7.0-py2.7.egg/transaction/_transaction.py", line 271, in commit
    self._commitResources()
  File "/srv/slapgrid/slappart16/srv/runner/software/cc627918c55102e3f1a6c6a0077f41bb/eggs/Products.TIDStorage-5.5.0-py2.7.egg/Products/TIDStorage/transaction_transaction.py", line 25
1, in _commitResources
    result = original__commitResources(self, *args, **kw)
  File "/srv/slapgrid/slappart16/srv/runner/software/cc627918c55102e3f1a6c6a0077f41bb/eggs/transaction-1.7.0-py2.7.egg/transaction/_transaction.py", line 416, in _commitResources
    reraise(t, v, tb)
  File "/srv/slapgrid/slappart16/srv/runner/software/cc627918c55102e3f1a6c6a0077f41bb/eggs/transaction-1.7.0-py2.7.egg/transaction/_transaction.py", line 390, in _commitResources
    rm.commit(self)
  File "/srv/slapgrid/slappart16/srv/runner/software/cc627918c55102e3f1a6c6a0077f41bb/eggs/ZODB-4.4.5-py2.7.egg/ZODB/Connection.py", line 582, in commit
    self._commit(transaction)
  File "/srv/slapgrid/slappart16/srv/runner/software/cc627918c55102e3f1a6c6a0077f41bb/eggs/ZODB-4.4.5-py2.7.egg/ZODB/Connection.py", line 630, in _commit
    raise ConflictError(object=obj)
ConflictError: database conflict error (oid 0x0c78a313, class erp5.portal_type.Sale Invoice Transaction)
------
******************* /nexedi/accounting_module/20220502-3DD4B45 localbuild restart because of ConflictError

2022-05-02 09:30:23,340 INFO InvoiceTransaction_selectInvoiceMovement, 37: <object object at 0x7f707a6e61f0> stopped sm
------
2022-05-02 09:30:23,342 INFO InvoiceTransaction_selectInvoiceMovement, 37: <object object at 0x7f707a6e61f0> stopped sm
------
2022-05-02 09:30:23,381 INFO InvoiceTransaction_selectDelivery, 27: <object object at 0x7f707a6e61f0> {<Sale Invoice Transaction at /nexedi/accounting_module/20220502-3DD4B45>: 1}

using json in 37b795fb was wrong,
because not all arguments can be converted to json (for example
DateTime instances)

This also enable the format using pprint.pformat for args, instead
of a simple str that was done in ActivityTool_getMessageList.

See merge request nexedi/erp5!1600

   The portal_skins was choosen to store the images to use proper http
cache.

   It is really not required, so we follow up the same as google oauth.

See merge request nexedi/erp5!1607

See merge request nexedi/erp5!1608