HOT-FIX 2: campos CharField não podem ser null (facepalm)

sapl/base/models.py

@@ -21,7 +21,6 @@ class CasaLegislativa(models.Model):
 
     codigo = models.CharField(max_length=100,
                               blank=True,
-                              null=True,
                               verbose_name=_('Codigo'))
     nome = models.CharField(max_length=100, verbose_name=_('Nome'))
     sigla = models.CharField(max_length=100, verbose_name=_('Sigla'))