Django - form field does not pass validation - django

Question

models.py
class Location(models.Model):
name = models.CharField(max_length=100, verbose_name=u"Локация", default=u'')
country = models.ForeignKey("Country")
class Country(models.Model):
name = models.CharField(max_length=50, verbose_name=u"Страна")
class Photo(models.Model):
location = models.ForeignKey(Location, null=True, verbose_name=u'Фото')
photo = models.ImageField(upload_to='photos', null=True)
forms.py
class LocationForm(forms.ModelForm):
class Meta:
model = Location
fields = ['name', 'country']
photos = MultiFileField(min_num=1, max_num=10)
def save(self, commit=True):
instance = super(LocationForm, self).save(commit)
for each in self.cleaned_data['photos']:
Photo.objects.create(photo=each, location=instance)
return instance
views.py
class AddLocationPageView(CreateView):
model = Location
form_class = LocationForm
template_name = 'add_location.html'
class BrowseLocationsPageView(ListView):
model = Country
context_object_name = 'countries'
template_name = "browse_locations.html"
add_location.html
<form action="" method="POST">{% csrf_token %}
{{ form|crispy }}
<button class="btn btn-default" type="submit">Add</button>
</form>
browse_locations.html
{% for country in countries %}
{{ country }}
{% endfor %}
While creating Location object the form field says: "Select a valid choice. That choice is not one of the available choices."
Of course, I do not have any choices, because the design is - if Country is absent in DB, it has to be created during Location creating, and in opposite case (Country is in DB, because someone created it before when he was creating Location) it has to be joined to Location.