Django:SQLIte的非空约束失败

下面是我的模型。运行

python manage.py migrate

django.db.utils.IntegrityError: NOT NULL constraint failed: app_project.description

模型如下：

from django.db import models


# Create your models here.

class Project(models.Model):
    title = models.CharField(max_length=100)
    description = models.TextField(max_length=2000, blank=True, default='')
    progress = models.FloatField(default=0)
    created_at = models.DateTimeField(auto_now_add=True)
    updated_at = models.DateTimeField(auto_now=True)

    def __str__(self):
        return self.title


class Task(models.Model):
    project = models.ForeignKey(Project, on_delete=models.CASCADE)
    title = models.CharField(max_length=100)
    severity = models.SmallIntegerField(default=0)
    open_date = models.DateTimeField()
    close_date = models.DateTimeField()
    status = models.SmallIntegerField(default=0)

    def __str__(self):
        return self.title

我在Django 1.10上更改为：

description = models.TextField(max_length=2000, blank=True, null=True, default='')

以允许数据库中的值为空

请参阅null和blank之间的差异，并将更改为：

description = models.TextField(max_length=2000, blank=True, null=True, default='')

以允许数据库中的值为空

请参见null和blank以及