Al intentar definir un boton para copiar un registro este me genera un Key error en todos los menus de mi modulo, el metodo lo he puesto asi:

@api.multi
def button_copy(self, default=None):
    self.ensure_one()
    default = dict(default or {})
    return super(Registro, self).copy(default)

Al entrar a los menus obtengo:

Traceback (most recent call last):
  File "/usr/lib/python2.7/dist-packages/odoo/http.py", line 638, in _handle_exception
    return super(JsonRequest, self)._handle_exception(exception)
  File "/usr/lib/python2.7/dist-packages/odoo/http.py", line 675, in dispatch
    result = self._call_function(**self.params)
  File "/usr/lib/python2.7/dist-packages/odoo/http.py", line 331, in _call_function
    return checked_call(self.db, *args, **kwargs)
  File "/usr/lib/python2.7/dist-packages/odoo/service/model.py", line 101, in wrapper
    return f(dbname, *args, **kwargs)
  File "/usr/lib/python2.7/dist-packages/odoo/http.py", line 324, in checked_call
    result = self.endpoint(*a, **kw)
  File "/usr/lib/python2.7/dist-packages/odoo/http.py", line 933, in __call__
    return self.method(*args, **kw)
  File "/usr/lib/python2.7/dist-packages/odoo/http.py", line 504, in response_wrap
    response = f(*args, **kw)
  File "/usr/lib/python2.7/dist-packages/odoo/addons/web/controllers/main.py", line 827, in search_read
    return self.do_search_read(model, fields, offset, limit, domain, sort)
  File "/usr/lib/python2.7/dist-packages/odoo/addons/web/controllers/main.py", line 846, in do_search_read
    Model = request.env[model]
  File "/usr/lib/python2.7/dist-packages/odoo/api.py", line 752, in __getitem__
    return self.registry[model_name]._browse((), self)
  File "/usr/lib/python2.7/dist-packages/odoo/modules/registry.py", line 174, in __getitem__
    return self.models[model_name]
KeyError: u'comprasmayores.registro'

y asi con cada menu... Alguna sugerencia o solucion del por que de esto??
Gracias de antemano, Saludos.