title: Django Migration: NOT NULL constraint failed
body: <p>here its my model code</p>
  
  <pre><code>class student(models.Model):
      name = models.CharField(max_length=100)
      age = models.IntegerField()
      available = models.BooleanField(default=False, blank=True)
  </code></pre>
  
  <p>In above model available is my new field, now I want to migrate database but it give me error, when I'm run following command</p>
  
  <pre><code>python manage.py migrate 
  
  Operations to perform:
    Apply all migrations: student
  Running migrations:
    Applying order.0004_auto_20150223_1758...Traceback (most recent call last):
    File "manage.py", line 10, in &lt;module&gt;
      execute_from_command_line(sys.argv)
    File "/home/nikhil/live-devEnv/local/lib/python2.7/site-packages/django/core/management/__init__.py", line 385, in execute_from_command_line
      utility.execute()
    File "/home/nikhil/live-devEnv/local/lib/python2.7/site-packages/django/core/management/__init__.py", line 377, in execute
      self.fetch_command(subcommand).run_from_argv(self.argv)
    File "/home/nikhil/live-devEnv/local/lib/python2.7/site-packages/django/core/management/base.py", line 288, in run_from_argv
      self.execute(*args, **options.__dict__)
    File "/home/nikhil/live-devEnv/local/lib/python2.7/site-packages/django/core/management/base.py", line 338, in execute
      output = self.handle(*args, **options)
    File "/home/nikhil/live-devEnv/local/lib/python2.7/site-packages/django/core/management/commands/migrate.py", line 160, in handle
      executor.migrate(targets, plan, fake=options.get("fake", False))
    File "/home/nikhil/live-devEnv/local/lib/python2.7/site-packages/django/db/migrations/executor.py", line 63, in migrate
      self.apply_migration(migration, fake=fake)
    File "/home/nikhil/live-devEnv/local/lib/python2.7/site-packages/django/db/migrations/executor.py", line 97, in apply_migration
      migration.apply(project_state, schema_editor)
    File "/home/nikhil/live-devEnv/local/lib/python2.7/site-packages/django/db/migrations/migration.py", line 107, in apply
      operation.database_forwards(self.app_label, schema_editor, project_state, new_state)
    File "/home/nikhil/live-devEnv/local/lib/python2.7/site-packages/django/db/migrations/operations/fields.py", line 37, in database_forwards
      field,
    File "/home/nikhil/live-devEnv/local/lib/python2.7/site-packages/django/db/backends/sqlite3/schema.py", line 167, in add_field
      self._remake_table(model, create_fields=[field])
    File "/home/nikhil/live-devEnv/local/lib/python2.7/site-packages/django/db/backends/sqlite3/schema.py", line 135, in _remake_table
      self.quote_name(model._meta.db_table),
    File "/home/nikhil/live-devEnv/local/lib/python2.7/site-packages/django/db/backends/schema.py", line 99, in execute
      cursor.execute(sql, params)
    File "/home/nikhil/live-devEnv/local/lib/python2.7/site-packages/django/db/backends/utils.py", line 81, in execute
      return super(CursorDebugWrapper, self).execute(sql, params)
    File "/home/nikhil/live-devEnv/local/lib/python2.7/site-packages/django/db/backends/utils.py", line 65, in execute
      return self.cursor.execute(sql, params)
    File "/home/nikhil/live-devEnv/local/lib/python2.7/site-packages/django/db/utils.py", line 94, in __exit__
      six.reraise(dj_exc_type, dj_exc_value, traceback)
    File "/home/nikhil/live-devEnv/local/lib/python2.7/site-packages/django/db/backends/utils.py", line 65, in execute
      return self.cursor.execute(sql, params)
    File "/home/nikhil/live-devEnv/local/lib/python2.7/site-packages/django/db/backends/sqlite3/base.py", line 485, in execute
      return Database.Cursor.execute(self, query, params)
  django.db.utils.IntegrityError: NOT NULL constraint failed: student.available
  </code></pre>
  
  <p>something wrong here please give me a solution for above problem.</p>