[web2py] [Error]TypeError: format requires a mapping

[Dewes]

Hello, I have the following table that worked in web2py 1.99.7, but now I 
upgraded to 2.2.1, and I got this error that I don't know how to solve:

Traceback (most recent call last):
  File 
"/home/dewes/Dropbox/desenvolvimento/novo_web2py/web2py/gluon/restricted.py", 
line 212, in restricted
    exec ccode in environment
  File 
"/home/dewes/Dropbox/desenvolvimento/novo_web2py/web2py/applications/normas/models/db.py"
 <http://localhost:8000/admin/default/edit/normas/models/db.py>, line 100, in 
<module>
    Field('grupo', db.auth_group, default=auth.user_group(auth.user_id), 
format='%(role)'),
  File "/home/dewes/Dropbox/desenvolvimento/novo_web2py/web2py/gluon/tools.py", 
line 2990, in user_group
    return self.id_group(self.user_group_role(user_id))
  File "/home/dewes/Dropbox/desenvolvimento/novo_web2py/web2py/gluon/tools.py", 
line 2997, in user_group_role
    return self.settings.create_user_groups % user
TypeError: format requires a mapping

db.define_table('normas',
    Field('titulo','string',label=T('Título')),
    Field('ementa','text',label=T('Ementa')),
    Field('tipo_norma',db.tipos,label=T('Tipo Norma')),
    Field('numero_norma','integer',label=T('Número')),
    Field('situacao',db.situacao,label=T('Situação')),
    Field('orgao_emissor','list:reference orgaos',label=T('Órgão Emissor')),
    Field('veiculo','string',label=T('Veículo de Publicação')),
    Field('numero_veiculo','integer',label=T('Número do Veículo')),
    Field('dt_emissao','date',label=T('Data de Emissão')),
    Field('dt_publicacao','date',label=T('Data de Publicação')),
    Field('conteudo','text',label=T('Conteúdo')),
    Field('arquivo1','upload',uploadseparate=True),
    Field('arquivo2','upload',uploadseparate=True),
    Field('arquivo3','upload',uploadseparate=True),
    Field('arquivo4','upload',uploadseparate=True),
    Field('arquivo5','upload',uploadseparate=True),
    Field('created_on', 'datetime', default=request.now),
    Field('created_by', db.auth_user, default=auth.user_id),
    Field('grupo', db.auth_group, default=auth.user_group(auth.user_id)),
    format='%(titulo)s'
)

Deleting the field Field('grupo', db.auth_group, 
default=auth.user_group(auth.user_id)), the error is gone, but I need this 
field, as a shortcut to restrict the "normas" (normative documents) to the 
group of people that created it, without going to the user that created and 
after the group of that user.

I have already tried to put in the Field something like format='%(role)s' or 
format='%(description)' but to no avail.

Thanks in advance.

More from error:

def user_group_role(self, user_id=None):
        if user_id:
            user = self.table_user()[user_id]
        else:
            user = self.user
        return self.settings.create_user_groups % user

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