ajax error

template

{% extends 'base/base.html' %}

{% block content %}

<form class="user" method="POST">
    <div class="card mb-4 py-3 border-left-primary">
        <h2 class="m-2 font-weight-bold text-primary"> Pre Testing Details</h2>
        <div class="dropdown-divider"></div>
        <div class="card-body">
            {% csrf_token %}
            <div class="row form-group">
                <div class="col-sm-6">
                    <label id="id_school" class="text-body ">School</label>
                   {{ form_enc.school }}
                </div>
                <div class="col-sm-3">
                    <label class="text-body ">Testing Date</label>
                    {{ form_enc.fecha_examen }}
                </div>
                <div class="col-sm-3">
                    <label class="text-body ">Graduation Date</label>
                    {{ form_enc.fecha_graduacion }}
                </div>
            </div>
            <div class="dropdown-divider"></div>
            <div class="row form-group">
                    <button type="submit" class="btn btn-success waves-effect waves-float mr-2"><span class="fa fa-save"></span> Save</button>
                    <a href="{% url 'testing:pretest_list' %}" class="btn btn-danger waves-effect waves-float"><span class="fa fa-undo"></span> Cancel</a>
            </div>
            <h4>Select Candidates</h1>
            <div class="table-responsive">
                <table width="100%" class="table table-bordered " id="dataTables-example" cellspacing="0">
                    <thead>
                    <tr>
                        <th>Id</th>
                        <th>Student Name</th>
                        <th>Rank</th>
                        <th>Test</th>
                        <th>Midterm</th>
                        <th>Paid</th>
                        <th>Order Belt</th>
                    </tr>
                    </thead>
                    <tbody>
                        {% for item in student %}
                        <tr id="{{ item.id }}">
                            <td>{{ item.id }}</td>
                            <td>{{ item.first_name }}, {{ item.first_last_name }}</td>
                            <td>{{ item.rank }}</td>
                            <td><input type="checkbox" name="test" id="test" /> </td>
                            <td><input type="checkbox" name="midterm" id="midterm" /> </td>
                            <td><input type="checkbox" name="pago" id="pago"/> </td>
                            <td><input type="checkbox" name="orderbelt" id="orderbelt" /> </td>
                        </tr>
                        {% endfor %}
                    </tbody>
                </table>
            </div>
        </div>
        <!--  botones aqui -->
    </div>
</form>
{% endblock %}


{% block js_page %}
<script>
    $(function () {

        $("#id_fecha_examen").datetimepicker({
                format: 'd/m/Y',
                timepicker:false
            });
        $("#id_fecha_graduacion").datetimepicker({
                format: 'd/m/Y',
                timepicker:false
            });

    $("#school").focus();
    });

    var token = $('input[name=csrfmiddlewaretoken]').val();
    $.ajaxSetup({
        beforeSend: function(xhr, settings) {
            if (!(/^http:.*/.test(settings.url) || /^https:.*/.test(settings.url))) {
                xhr.setRequestHeader("X-CSRFToken", token);
            }
        }
    });


$('form').on('submit', function(e) {
     e.preventDefault();
     var $dataElements = $('#dataTables-example').find('td'),
      data = [];

    $.each($dataElements, function(i, elem){
        data.push($(elem).html());
    });
    var template="{% url 'testing:pretest_list' %}";
    $.ajax({
        type: "POST",
        url: template,
        data: {data:JSON.stringify(data)},
        beforeSend: function(xhr,settings){
          $.ajaxSettings.beforeSend(xhr,settings);
        },
        success: function(response){
          console.log(response);
          cerrar_modal();
          window.location.reload()
          //alert(response);
          var tipo=(response.startsWith('Escuela no existe') ? 'red':'green' );
          mensaje(response,tipo);
        },
        error: function(jqXHR, textStatus, errorThrow){
          console.log(textStatus, errorThrow);
          mensaje(errorThrow,'red');
          cerrar_modal();
        }
      });

});

</script>
{% endblock js_page %}




VIEW

def pretest(request, pretest_id=None):
	template_name="testing/pretesting_form.html"
	rango = ProgramaRank.objects.filter(activo=True).order_by('pk')
	form_pretest ={}
	contexto = {}

	if request.method=="GET":
		form_pretest = PreTestEncForm()
		enc= PreTestEnc.objects.filter(school_id=pretest_id).first()
		if enc:
			det=PreTestDet.objects.filter(pretestenc = enc)
			student = People.objects.filter(school_id=enc.school_id)
			if enc.fecha_examen:
				fecha_examen = datetime.date.isoformat(enc.fecha_examen)
			else:
				fecha_examen = 0
			if enc.fecha_graduacion:
				fecha_graduacion = datetime.date.isoformat(enc.fecha_graduacion)
			else:
				fecha_graduacion = 0
			e={
				'school': enc.school,
				'fecha_examen': fecha_examen,
				'fecha_graduacion': fecha_graduacion,
			}
			form_pretest= PreTestEncForm(e)
		else:
			det = None
			student = People.objects.all()

		contexto = {'rango':rango, 'encabezado':enc, 'detalle':det,'student':student, 'form_enc':form_pretest}

	if request.method=="POST":
		school = request.POST.get("school")
		fecha_examen = request.POST.get("fecha_examen")
	#	fecha_examen = datetime.datetime.strptime(fecha_examen, "%d/%m/%Y")
		fecha_graduacion = request.POST.get("fecha_graduacion")
	#	fecha_graduacion = datetime.datetime.strptime(fecha_graduacion, "%d/%m/%Y")
		table = request.POST.get("data")


		if not pretest_id:
			enc = PreTestEnc(
				school = school,
				fecha_examen = fecha_examen,
				fecha_graduacion = fecha_graduacion
			)
			if enc:
				enc.save()
				pretest_id = enc.id

		else:
			school = School.objects.filter(pk = school).first()
			enc= PreTestEnc.objects.filter(pk=pretest_id).first()
			if enc:
				enc.school = school
				enc.fecha_examen = fecha_examen
				enc.fecha_graduacion = fecha_graduacion
				enc.save()

		if not pretest_id:
			return redirect("testing:pretest_list")

		for x in table:
			people = request.POST.get("id_student")
			rank = request.POST.get("student.rank")
			test = request.POST.get("test")
			midterm = request.POST.get("midterm")
			paid = request.POST.get("paid")
			orderbelt = request.POST.get("orderbelt")
			det = PreTestDet(
				pretestenc = enc,
				people = people,
				rangoactual = rank,
				test = test,
				midterm = midterm,
				pago = paid,
				order_belt = orderbelt
			)
		#	if det:
				#det.save()

		return redirect("testing:pretest_list")

	return render(request, template_name, contexto)