title: Django users: get list of group, or how to convert MultipleChoiceField to ChoiceField
body: <p>I've searched similar topics but haven't found what I need..</p>
  
  <p>I extended Users model with UserAttributes model, some additional fields added and etc.. now I'm trying to make ModelForm out this.. so I have a little problem in here.. </p>
  
  <p>I WANT TO list groups as a ChoiceField not a MultipleChoiceField.. It's a requirement by specification so it must be so.</p>
  
  <p>so here's the code..</p>
  
  <pre><code>from django.forms               import ModelForm
  from django.contrib.auth.models import User
  from helpdesk.models.userattributes      import *
  from django.utils.translation import ugettext as _
  
  class SettingsOperatorsForm(ModelForm):
  
  
      groups = forms.ChoiceField(
          label=_(u'Rights'),
          required=True,
          choices=["what's in here?"]
      )
  
      class Meta:
          model   = UserAttributes
          fields  = ('first_name', 'last_name', 'job_title', 'email', 'password', 'is_active', 'groups'  )
  </code></pre>
  
  <p>there's auth_group table in database, so i tried to make it like this , but I've got a no form displayed at all:</p>
  
  <pre><code>from django.contrib.auth.models import User, Group
  
  groups = forms.ChoiceField(
      label=_(u'Rights'),
      required=True,
      choices=Group.objects.all()
  )
  </code></pre>
  
  <p>I think it's better would be just to convert multipleChoiceField to ChoiceField</p>
  
  <p>in plain talk:</p>
  
  <p><img src="https://i.imgur.com/qGUBT.png" alt="alt text"></p>
  
  <p>should become just SELECT box.</p>