Corrige o bug

sapl/sessao/migrations/0012_auto_20170815_1244.py

@@ -0,0 +1,21 @@
+# -*- coding: utf-8 -*-
+# Generated by Django 1.9.13 on 2017-08-15 12:44
+from __future__ import unicode_literals
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('sessao', '0011_auto_20170814_1849'),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name='tiporesultadovotacao',
+            name='natureza',
+            field=models.CharField(blank=True, choices=[('A', 'Aprovado'), ('R', 'Rejeitado')], default='', max_length=100, verbose_name='Natureza do Tipo'),
+            preserve_default=False,
+        ),
+    ]

sapl/sessao/models.py

@@ -371,9 +371,8 @@ class TipoResultadoVotacao(models.Model):
     nome = models.CharField(max_length=100, verbose_name=_('Nome do Tipo'))
     natureza = models.CharField(max_length=100,
                                 blank=True,
-                                null=True,
                                 choices=(('A', 'Aprovado'),
-                                          ('R', 'Rejeitado')),
+                                         ('R', 'Rejeitado')),
                                 verbose_name=_('Natureza do Tipo'))
 
     class Meta: