Error that field is required when there is no field empty

Question

This is my view:

class EditInventoryView(UpdateView):
    model = Inventory
    form_class = InventoryForm
    template_name = 'inventory/detail.html'

    def get(self, request, **kwargs):
        object = super(EditInventoryView, self).get_object()
        formset = self.form_class(instance=object)      
        context = {
            'form': formset,
            'item': object,
        }
        return render(request, 'inventory/detail.html', context) 

    def post(self, request, **kwargs):
        object = super(EditInventoryView, self).get_object()
        form = self.form_class(request.POST, request.FILES, instance=object)
        context = {
            'form': form, 
            'item': object,
        }
        if form.is_valid():
            object = form.save()
            messages.success(request, "Saved %s!" % object)
            return redirect(object.get_absolute_url())
        else:
            messages.error(request, 'Change a few things up and try submitting again. %s' % form.errors)
            return render(request, 'inventory/detail.html', context)

When I submit it this is always the error message:

Change a few things up and try submitting again. <ul class="errorlist"><li>connections<ul class="errorlist"><li>This field is required.</li></ul></li></ul>

I know this form used to work, but maybe I changed something in the model that is making it not work.

The model:

class Inventory(MPTTModel):
    type = models.ForeignKey('inventory_types.Type', db_column='type_id')
    name = models.TextField(db_column='value')
    asset_tag = models.IntegerField(db_column='asset_tag', unique=True, null=True, blank=True)
    parent = TreeForeignKey('self', null=True, blank=True, related_name='children')

    connections = models.ManyToManyField('self', related_name='connections')

    objects = InventoryManager()
    tree = TreeManager()

    class Meta: 
        db_table = 'inventory'
        verbose_name_plural = 'Inventory Items'

    class MPTTMeta:
        order_insertion_by = ['type']

    def __unicode__(self):
        return u'[%s] %s' % (self.type.name, self.name)

    def get_related_descendants(self, include_self=False):
        return self.get_descendants(include_self=include_self) \
                   .select_related('type', 'parent').prefetch_related('connections')

    def get_related_ancestors(self, include_self=False):
        return self.get_ancestors(include_self=include_self) \
                   .select_related('type', 'parent').prefetch_related('connections')

    def get_absolute_url(self):
        return reverse('inventory:view', args=(self.id,))

    def add_anc_type(self, id, all_types, all_objects):
        if id is not self.id: all_types.add(all_objects[id][1])
        if all_objects[id][0] is not None:
            self.add_anc_type(all_objects[id][0], all_types, all_objects)

    def add_desc_type(self, id, all_types, all_objects):
        if id not in all_objects: return
        for child, type_id in all_objects[id].iteritems():
            all_types.add(type_id)
            self.add_desc_type(child, all_types, all_objects)

Answer 1

Setting blank=True on connection will remove the form's error. If you want the file to be nullable in the DB then you can set null=True or just establish a default value.

In order to remove the form error you just need to do this:

connections = models.ManyToManyField('self', related_name='connections', blank=True)

Hope this helps!