【django】フィールドのchoicesで選択肢から選ぶ方法

class Blog(models.Model):
    LANG_TYPES = (
        ('py', 'Python'),
        ('js', 'Javascript'),
        ('css', 'CSS'),
        ('html', 'HTML'),
    )
    title = models.CharField(max_length=200)
    content = models.TextField(blank=True)
    lang_type = models.CharField(max_length=50, choices=LANG_TYPES, blank=True) # 追加
    updated_at = models.DateTimeField(auto_now=True)
    created_at = models.DateTimeField(auto_now_add=True)

    def __str__(self):
        return self.title

    class Meta:
        db_table = 'blogs'

python manage.py makemigrations blog
python manage.py migrate

You are trying to add a non-nullable field 'lang_type' to blog 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 with a null value for this column)
 2) Quit, and let me add a default in models.py