####views.py
def pg_session_addedcost(request, pk = 1):
    user = request.user

    if not user.is_authenticated:
        return redirect('autherror')

    curSession = Session.objects.get(id = pk)

    if request.method == "POST":
        newAddedCostForm = AddedCostForm(request.POST)
        if newAddedCostForm.is_valid():
            newAddedCost = AddedCost(
                comment=newAddedCostForm.cleaned_data['comment'],
                session=curSession,
                image=newAddedCostForm.cleaned_data['image'],
                cost=newAddedCostForm.cleaned_data['cost'],
            )
            newAddedCost.save()
        else:
            print(newAddedCostForm.errors)

    content = {
        'user':user,
        'session':curSession,
        'form':AddedCostForm(),
        'addedcost':AddedCost.objects.filter(session = curSession),
    }

    return render(request, 'staffapp/pg_addedcost.html',content)


###HTML

{% load widget_tweaks %}
<form method="POST">
                                {% csrf_token %}

                                {% render_field form.image %}<br>
                                {% render_field form.cost %}<br>
                                {% render_field form.comment %}<br>

                                <button type="submit">
                                    Добавить
                                </button>
                            </form>

###Текст ошибки
<ul class="errorlist"><li>image<ul class="errorlist"><li>Обязательное поле.</li></ul></li></ul>