title: Django SplitDateTime widget throws 'list' object has no attribute 'strip'
body: <p>I am trying to create event with start date-time and end date-time with django. In the forms I've tried to seperate the date and time inputs with AdminSPlitDateTime widget (I'd like to have some JS for the input.) When I tried to create an event django gives me "'list' object has no attribute 'strip'" error. Also happens with SplitDateTimeWidget.</p>
  
  <p>When I removed the widget or use DateTimeInput widget (no split) everything works as expected. But User can confuse to enter the proper format for date time. SO I want to user AdminSplitDateTime.</p>
  
  <p>It must be something with spliting the date and time with widgets but I couldn't figure a way to solve this.</p>
  
  <p>Using Python 3.7
  django 2.2.7
  pipenv 2018.11.26</p>
  
  <p>my Model is</p>
  
  <pre><code>class Event(models.Model):
      event_start = models.DateTimeField()
      event_end = models.DateTimeField()
      notes = models.CharField(max_length=140, null=True, blank=True)
      hasta = models.ForeignKey(Hasta, on_delete=models.CASCADE)
      doktor = models.ForeignKey(User, on_delete=models.CASCADE)
  
  
  
      def __str__(self):
          return f'{self.event_start} -- {self.event_end}'
  
      class Meta:
          ordering = ['event_start'] 
  </code></pre>
  
  <p>my Form class is:</p>
  
  <pre><code>class EventCreateForm(ModelForm):
      event_start = forms.DateTimeField(widget= admin_widgets.AdminSplitDateTime())
      event_end = forms.DateTimeField(widget=admin_widgets.AdminSplitDateTime())
  
      def __init__(self, *args, **kwargs):
          """this whole thing is for filtering the hasta objects. User can only create an event with his patients."""
          self.user = kwargs.pop('user')
          super().__init__(*args, **kwargs)
          self.fields['hasta'].queryset = Hasta.objects.filter(doktor_id=self.user.id)
  
      class Meta:
          model = Event
          fields = [
              'event_start',
              'event_end',
              'notes',
              'hasta',
          ]
          labels = {
              'event_start': _('Randevu Başlangıç Tarihi'),
              'event_end': _('Randevu Bitiş Tarihi'),
              'notes': _('Notlar')
  
          } 
  </code></pre>
  
  <p>And my View class is:</p>
  
  <pre><code>class EventCreateView(LoginRequiredMixin, CreateView):
      model = Event
      template_name = 'create_event.html'
      form_class = EventCreateForm
      success_url = '/randevu'
  
      def get_form_kwargs(self):
          """This adds the user object to the kwargs and it will be used in create event form to filter
          the patients of the current user"""
          kwargs = super(EventCreateView, self).get_form_kwargs()
          kwargs.update({'user': self.request.user})
          return kwargs
  
      def form_valid(self, form):
          """This adds the current user id to the created event"""
          form.instance.doktor = self.request.user
          form.save()
          messages.success(self.request, f"randevu Kaydedildi!")
          return super().form_valid(form)
  </code></pre>
  
  <p>I am getting the below error;</p>
  
  <pre><code>AttributeError: 'list' object has no attribute 'strip'
  [19/Nov/2019 13:34:11] "POST /randevu/yeni_randevu/ HTTP/1.1" 500 117105
  Internal Server Error: /randevu/yeni_randevu/
  Traceback (most recent call last):
    File "C:\Users\alper\.virtualenvs\sekreter-1XQSW2uk\lib\site-packages\django\core\handlers\exception.py", line 34, in inner
      response = get_response(request)
    File "C:\Users\alper\.virtualenvs\sekreter-1XQSW2uk\lib\site-packages\django\core\handlers\base.py", line 115, in _get_response
      response = self.process_exception_by_middleware(e, request)
    File "C:\Users\alper\.virtualenvs\sekreter-1XQSW2uk\lib\site-packages\django\core\handlers\base.py", line 113, in _get_response
      response = wrapped_callback(request, *callback_args, **callback_kwargs)
    File "C:\Users\alper\.virtualenvs\sekreter-1XQSW2uk\lib\site-packages\django\views\generic\base.py", line 71, in view
      return self.dispatch(request, *args, **kwargs)
    File "C:\Users\alper\.virtualenvs\sekreter-1XQSW2uk\lib\site-packages\django\contrib\auth\mixins.py", line 52, in dispatch
      return super().dispatch(request, *args, **kwargs)
    File "C:\Users\alper\.virtualenvs\sekreter-1XQSW2uk\lib\site-packages\django\views\generic\base.py", line 97, in dispatch
      return handler(request, *args, **kwargs)
    File "C:\Users\alper\.virtualenvs\sekreter-1XQSW2uk\lib\site-packages\django\views\generic\edit.py", line 172, in post
      return super().post(request, *args, **kwargs)
    File "C:\Users\alper\.virtualenvs\sekreter-1XQSW2uk\lib\site-packages\django\views\generic\edit.py", line 141, in post
      if form.is_valid():
    File "C:\Users\alper\.virtualenvs\sekreter-1XQSW2uk\lib\site-packages\django\forms\forms.py", line 185, in is_valid
      return self.is_bound and not self.errors
    File "C:\Users\alper\.virtualenvs\sekreter-1XQSW2uk\lib\site-packages\django\forms\forms.py", line 180, in errors
      self.full_clean()
    File "C:\Users\alper\.virtualenvs\sekreter-1XQSW2uk\lib\site-packages\django\forms\forms.py", line 381, in full_clean
      self._clean_fields()
    File "C:\Users\alper\.virtualenvs\sekreter-1XQSW2uk\lib\site-packages\django\forms\forms.py", line 399, in _clean_fields
      value = field.clean(value)
    File "C:\Users\alper\.virtualenvs\sekreter-1XQSW2uk\lib\site-packages\django\forms\fields.py", line 148, in clean
      value = self.to_python(value)
    File "C:\Users\alper\.virtualenvs\sekreter-1XQSW2uk\lib\site-packages\django\forms\fields.py", line 462, in to_python
      result = super().to_python(value)
    File "C:\Users\alper\.virtualenvs\sekreter-1XQSW2uk\lib\site-packages\django\forms\fields.py", line 379, in to_python
      value = value.strip()
  AttributeError: 'list' object has no attribute 'strip'
  
  </code></pre>