UnicodeEncodeError when merging pickings with special characters

When trying to merge two pickings that have the character ü in the Notes, the following error is thrown.

Last revision No. & ID :Bazaar Package not Found !Traceback (most recent call last):
  File "/usr/lib/pymodules/python2.7/openerp/wsgi/core.py", line 79, in xmlrpc_return
    result = openerp.netsvc.dispatch_rpc(service, method, params)
  File "/usr/lib/pymodules/python2.7/openerp/netsvc.py", line 360, in dispatch_rpc
    result = ExportService.getService(service_name).dispatch(method, params)
  File "/usr/lib/pymodules/python2.7/openerp/service/web_services.py", line 586, in dispatch
    res = fn(db, uid, *params)
  File "/usr/lib/pymodules/python2.7/openerp/osv/osv.py", line 121, in wrapper
    return f(self, dbname, *args, **kwargs)
  File "/usr/lib/pymodules/python2.7/openerp/osv/osv.py", line 176, in execute
    res = self.execute_cr(cr, uid, obj, method, *args, **kw)
  File "/usr/lib/pymodules/python2.7/openerp/osv/osv.py", line 164, in execute_cr
    return getattr(object, method)(cr, uid, *args, **kw)
  File "/usr/lib/pymodules/python2.7/openerp/addons/stock_merge_picking/wizard/merge_picking.py", line 222, in do_merge
    linenote += ", Notes: " + str(merge.note)
UnicodeEncodeError: 'ascii' codec can't encode character u'\xfc' in position 16: ordinal not in range(128)

Apparently merge.note is in unicode, the conversion to ascii fails when it meets the non-ascii character ü.

My fix was to use tools.ustr instead of str(), see the attached patch for the wizzard. I am sure other parts of the addon are affected but unfortunately I do not have the time to look into it in depth.

I also saw that stock_merge_pickings has been deprecated, nonetheless I figured you might want to include that in your test cases. Do you have any idea if the replacement stock_picking_groups is ready for production use and if it could run in OpenERP 6.1.x?