Size should be optional.

bikeshop_project/bike/migrations/0003_auto_20170105_1405.py

@@ -0,0 +1,20 @@
+# -*- coding: utf-8 -*-
+# Generated by Django 1.10.4 on 2017-01-05 14:05
+from __future__ import unicode_literals
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('bike', '0002_auto_20170105_0238'),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name='bike',
+            name='size',
+            field=models.TextField(blank=True, choices=[('C', 'child'), ('M', 'medium'), ('L', 'large'), ('XL', 'extra large')], max_length=2, null=True),
+        ),
+    ]

bikeshop_project/bike/models.py

@@ -52,7 +52,7 @@ class Bike(models.Model):
 
     colour = models.TextField(blank=False, null=False)
     make = models.TextField(blank=False, null=False)
-    size = models.TextField(choices=size_choices, max_length=2)
+    size = models.TextField(choices=size_choices, blank=True, null=True, max_length=2)
     serial_number = models.TextField(blank=False, null=False)
     source = models.TextField(blank=False, null=False, choices=source_choices)
     stripped = models.NullBooleanField()
@@ -72,7 +72,7 @@ class Bike(models.Model):
 
     def can_assessed(self):
         return self.colour is not None and self.make is not None and self.size is not None and self.source is not None \
-               and self.price is not None
+               and self.price is not None and self.size is not None
 
     def can_available(self):
         return self.stolen is not None and self.cpic_searched_at is not None and self.serial_number is not None