title: Django error when migrating (int() and datetime.datetime)
body: <p>I think it's a basic mistake, but I'm trying to do some tests but now can't migrate the content. I've made the <code>python manage.py makemigrations</code> normally but when using 'migrate' it appears that message error:</p>
  
  <pre><code>C:\P3\P3\urls.py:21: RemovedInDjango110Warning: Support for string view arguments to url() is deprecated and will be removed in Django 1.10 (got quizzy.views.primeraprox). Pass the callable instead.
    url(r'^primaprox/', 'quizzy.views.primeraprox'),
  
  Operations to perform:
    Apply all migrations: contenttypes, admin, sessions, quizzy, auth
  Running migrations:
    Rendering model states... DONE
    Applying quizzy.0002_auto_20160313_1718...Traceback (most recent call last):
    File "manage.py", line 10, in &lt;module&gt;
      execute_from_command_line(sys.argv)
    File "C:\Python\lib\site-packages\django-1.9.1-py3.5.egg\django\core\management\__init__.py", line 353, in execute_from_command_line
      utility.execute()
    File "C:\Python\lib\site-packages\django-1.9.1-py3.5.egg\django\core\management\__init__.py", line 345, in execute
      self.fetch_command(subcommand).run_from_argv(self.argv)
    File "C:\Python\lib\site-packages\django-1.9.1-py3.5.egg\django\core\management\base.py", line 348, in run_from_argv
      self.execute(*args, **cmd_options)
    File "C:\Python\lib\site-packages\django-1.9.1-py3.5.egg\django\core\management\base.py", line 399, in execute
      output = self.handle(*args, **options)
    File "C:\Python\lib\site-packages\django-1.9.1-py3.5.egg\django\core\management\commands\migrate.py", line 200, in handle
      executor.migrate(targets, plan, fake=fake, fake_initial=fake_initial)
    File "C:\Python\lib\site-packages\django-1.9.1-py3.5.egg\django\db\migrations\executor.py", line 92, in migrate
      self._migrate_all_forwards(plan, full_plan, fake=fake, fake_initial=fake_initial)
    File "C:\Python\lib\site-packages\django-1.9.1-py3.5.egg\django\db\migrations\executor.py", line 121, in _migrate_all_forwards
      state = self.apply_migration(state, migration, fake=fake, fake_initial=fake_initial)
    File "C:\Python\lib\site-packages\django-1.9.1-py3.5.egg\django\db\migrations\executor.py", line 198, in apply_migration
      state = migration.apply(state, schema_editor)
    File "C:\Python\lib\site-packages\django-1.9.1-py3.5.egg\django\db\migrations\migration.py", line 123, in apply
      operation.database_forwards(self.app_label, schema_editor, old_state, project_state)
    File "C:\Python\lib\site-packages\django-1.9.1-py3.5.egg\django\db\migrations\operations\fields.py", line 62, in database_forwards
      field,
    File "C:\Python\lib\site-packages\django-1.9.1-py3.5.egg\django\db\backends\base\schema.py", line 382, in add_field
      definition, params = self.column_sql(model, field, include_default=True)
    File "C:\Python\lib\site-packages\django-1.9.1-py3.5.egg\django\db\backends\base\schema.py", line 145, in column_sql
      default_value = self.effective_default(field)
    File "C:\Python\lib\site-packages\django-1.9.1-py3.5.egg\django\db\backends\base\schema.py", line 210, in effective_default
      default = field.get_db_prep_save(default, self.connection)
    File "C:\Python\lib\site-packages\django-1.9.1-py3.5.egg\django\db\models\fields\related.py", line 912, in get_db_prep_save
      return self.target_field.get_db_prep_save(value, connection=connection)
    File "C:\Python\lib\site-packages\django-1.9.1-py3.5.egg\django\db\models\fields\__init__.py", line 728, in get_db_prep_save
      prepared=False)
    File "C:\Python\lib\site-packages\django-1.9.1-py3.5.egg\django\db\models\fields\__init__.py", line 968, in get_db_prep_value
      value = self.get_prep_value(value)
    File "C:\Python\lib\site-packages\django-1.9.1-py3.5.egg\django\db\models\fields\__init__.py", line 976, in get_prep_value
      return int(value)
  TypeError: int() argument must be a string, a bytes-like object or a number, not 'datetime.datetime'
  </code></pre>
  
  <p>Also, what's the problem with the URL?</p>
  
  <p>My models.py look like this:</p>
  
  <pre><code>from django.db import models
  from django.utils import timezone
  
  class Questions(models.Model):
      content = models.CharField(max_length=200)
      pub_date = models.DateTimeField('datetime field', default=True)
  
      def __str__(self):
          return self.content
  
  class Answer(models.Model):
      answer_text = models.CharField(max_length=200)
      first_field = models.CharField(max_length=150)
      question = models.ManyToManyField(Questions)
  
      def __str__(self):
          return self.answer_text
  </code></pre>
  
  <p>I just want to be able to make the migration, and can't figure out why Django is giving this error about 'datetime.datetime'. I would really appreciate any help. Thank you.</p>
  
  <p><strong>EDIT 1</strong>: I changed the pub_date field. Then 'makemigrations' and it returns that:</p>
  
  <pre><code>C:\P3&gt;python manage.py makemigrations
  C:\P3\P3\urls.py:21: RemovedInDjango110Warning: Support for string view arguments to url() is deprecated and will be removed in Django 1.10 (got quizzy.views.primeraprox). Pass the callable instead.
    url(r'^primaprox/', 'quizzy.views.primeraprox'),
  
  System check identified some issues:
  
  WARNINGS:
  quizzy.Questions.pub_date: (fields.W161) Fixed default value provided.
          HINT: It seems you set a fixed date / time / datetime value as default for this field. This may not be what you want. If you want to have the current date as default, use `django.utils.timezone.now`
  Migrations for 'quizzy':
    0012_auto_20160313_1810.py:
      - Alter field pub_date on questions
  </code></pre>
  
  <p>Then when I run 'migrate' again, the error message is the same. What is happening? Thank you</p>
  
  <p><strong>EDIT 2</strong>: If you are requesting the above text of the 'make migration' is this one:</p>
  
  <pre><code>C:\P3&gt;python manage.py makemigrations
  C:\P3\P3\urls.py:21: RemovedInDjango110Warning: Support for string view arguments to url() is deprecated and will be removed in Django 1.10 (got quizzy.views.primeraprox). Pass the callable instead.
    url(r'', 'quizzy.views.primeraprox'),
  
  You are trying to add a non-nullable field 'quiz' to questions without a default; we can't do that (the database needs something to populate existing rows).
  Please select a fix:
   1) Provide a one-off default now (will be set on all existing rows)
   2) Quit, and let me add a default in models.py
  Select an option: 1
  Please enter the default value now, as valid Python
  The datetime and django.utils.timezone modules are available, so you can do e.g. timezone.now()
  &gt;&gt;&gt; timezone.now()
  Migrations for 'quizzy':
    0002_auto_20160313_1718.py:
      - Create model Quiz
      - Add field quiz to questions
  </code></pre>
  
  <p>this belongs to some changes I made but now I've deleted it, maybe there could be the error. </p>
  
  <p><strong>EDIT 3</strong>: with the pub_date set to (auto_now=True), the complete migration is this:</p>
  
  <pre><code>C:\P3&gt;python manage.py migrate
  C:\P3\P3\urls.py:21: RemovedInDjango110Warning: Support for string view arguments to url() is deprecated and will be removed in Django 1.10 (got quizzy.views.primeraprox). Pass the callable instead.
    url(r'^primaprox/', 'quizzy.views.primeraprox'),
  
  Operations to perform:
    Apply all migrations: quizzy, contenttypes, sessions, auth, admin
  Running migrations:
    Rendering model states... DONE
    Applying quizzy.0002_auto_20160313_1718...Traceback (most recent call last):
    File "manage.py", line 10, in &lt;module&gt;
      execute_from_command_line(sys.argv)
    File "C:\Python\lib\site-packages\django-1.9.1-py3.5.egg\django\core\management\__init__.py", line 353, in execute_from_command_line
      utility.execute()
    File "C:\Python\lib\site-packages\django-1.9.1-py3.5.egg\django\core\management\__init__.py", line 345, in execute
      self.fetch_command(subcommand).run_from_argv(self.argv)
    File "C:\Python\lib\site-packages\django-1.9.1-py3.5.egg\django\core\management\base.py", line 348, in run_from_argv
      self.execute(*args, **cmd_options)
    File "C:\Python\lib\site-packages\django-1.9.1-py3.5.egg\django\core\management\base.py", line 399, in execute
      output = self.handle(*args, **options)
    File "C:\Python\lib\site-packages\django-1.9.1-py3.5.egg\django\core\management\commands\migrate.py", line 200, in handle
      executor.migrate(targets, plan, fake=fake, fake_initial=fake_initial)
    File "C:\Python\lib\site-packages\django-1.9.1-py3.5.egg\django\db\migrations\executor.py", line 92, in migrate
      self._migrate_all_forwards(plan, full_plan, fake=fake, fake_initial=fake_initial)
    File "C:\Python\lib\site-packages\django-1.9.1-py3.5.egg\django\db\migrations\executor.py", line 121, in _migrate_all_forwards
      state = self.apply_migration(state, migration, fake=fake, fake_initial=fake_initial)
    File "C:\Python\lib\site-packages\django-1.9.1-py3.5.egg\django\db\migrations\executor.py", line 198, in apply_migration
      state = migration.apply(state, schema_editor)
    File "C:\Python\lib\site-packages\django-1.9.1-py3.5.egg\django\db\migrations\migration.py", line 123, in apply
      operation.database_forwards(self.app_label, schema_editor, old_state, project_state)
    File "C:\Python\lib\site-packages\django-1.9.1-py3.5.egg\django\db\migrations\operations\fields.py", line 62, in database_forwards
      field,
    File "C:\Python\lib\site-packages\django-1.9.1-py3.5.egg\django\db\backends\base\schema.py", line 382, in add_field
      definition, params = self.column_sql(model, field, include_default=True)
    File "C:\Python\lib\site-packages\django-1.9.1-py3.5.egg\django\db\backends\base\schema.py", line 145, in column_sql
      default_value = self.effective_default(field)
    File "C:\Python\lib\site-packages\django-1.9.1-py3.5.egg\django\db\backends\base\schema.py", line 210, in effective_default
      default = field.get_db_prep_save(default, self.connection)
    File "C:\Python\lib\site-packages\django-1.9.1-py3.5.egg\django\db\models\fields\related.py", line 912, in get_db_prep_save
      return self.target_field.get_db_prep_save(value, connection=connection)
    File "C:\Python\lib\site-packages\django-1.9.1-py3.5.egg\django\db\models\fields\__init__.py", line 728, in get_db_prep_save
      prepared=False)
    File "C:\Python\lib\site-packages\django-1.9.1-py3.5.egg\django\db\models\fields\__init__.py", line 968, in get_db_prep_value
      value = self.get_prep_value(value)
    File "C:\Python\lib\site-packages\django-1.9.1-py3.5.egg\django\db\models\fields\__init__.py", line 976, in get_prep_value
      return int(value)
  TypeError: int() argument must be a string, a bytes-like object or a number, not 'datetime.datetime'
  </code></pre>
  
  <p><strong>EDIT 4 ( migration )</strong>: the migration file contains that:</p>
  
  <pre><code>class Migration(migrations.Migration):
  
      dependencies = [
          ('quizzy', '0001_initial'),
      ]
  
      operations = [
          migrations.CreateModel(
              name='Quiz',
              fields=[
                  ('id', models.AutoField(auto_created=True, primary_key=True, serialize=False, verbose_name='ID')),
                  ('name', models.TextField(default='true', max_length=200)),
              ],
          ),
          migrations.AddField(
              model_name='questions',
              name='quiz',
              field=models.ForeignKey(default=datetime.datetime(2016, 3, 13, 16, 18, 27, 23857, tzinfo=utc), on_delete=django.db.models.deletion.CASCADE, to='quizzy.Quiz'),
              preserve_default=False,
          ),
      ]
  </code></pre>