title: Django choices field in form
body: <p>I have two tables:</p>
  <pre><code>class Career(models.Model):    
      title = models.CharField(max_length=300)
      job_type = models.CharField(max_length=20, blank=False, default=None)
      location = models.CharField(max_length=200, blank=False, default=None)
      description = RichTextUploadingField(max_length=227, blank=False, default=None)
  
  class ApplyJob(models.Model):
      first_name = models.CharField(verbose_name=_('First Name'), max_length=100)
      last_name = models.CharField(verbose_name=_('Last Name'), max_length=100)
      email = models.EmailField(verbose_name=_('Email'), max_length=200)
      position = models.CharField(verbose_name=_('Position'), max_length=40)
      apply = models.ManyToManyField(Career, default=None, blank=True)
  </code></pre>
  <p>And a ModelForm:</p>
  <pre><code>class Meta:
      model = ApplyJob
      fields = ('first_name', 'last_name', 'email','position', 'message')
      widgets = {
           'position': forms.Select(choices=CHOICES, attrs={'class': 'form-control'})}
  </code></pre>
  <p>I want to add choices selection in <code>position</code> with values from Career table, so itried to query Career table to get all values. So i tried <code>CHOICES = Career.objects.values_list('title', flat=True).distinct()</code> but i got an <code>Exception Error: too many values to unpack (expected 2)</code></p>
  <p>Any ideas on what the problem is about?
  Thank you!</p>