coercing to Unicode: need string or buffer, Task found

Цікаву САБЖ помилку дебажив.

class Task(models.Model):
    name = models.CharField(max_length=120)
    description = models.TextField()
    price = models.DecimalField(max_digits=5, decimal_places=2)
    buyer = models.ForeignKey(User, related_name='buyer')
    created_at = models.DateTimeField(auto_now_add=True)
    updated_at = models.DateTimeField(auto_now=True)
    def __unicode__(self):
        return self.name

class TaskStatus(models.Model):
    POSTED, ASSIGNED, COMPLETED, CLOSED = range(1,5)
    TASK_STATUS_VALUES = (
        (POSTED, 'Posted'),
        (ASSIGNED, 'Assigned'),
        (COMPLETED, 'Completed'),
        (CLOSED, 'Closed'),
    )
    task = models.ForeignKey(Task)
    task_status = models.IntegerField(choices=TASK_STATUS_VALUES, blank=True, null=True)
    provider = models.ForeignKey(User, blank=True, null=True)
    created_at = models.DateTimeField(auto_now_add=True)
    def __unicode__(self):
        return self.task

лікується:

    def __unicode__(self):
        return unicode(self.task)