Django client does not delete in test

Hi I am now using Django REST3.5.3. I can do CRUD perfectly fine with browsable API.

My problem is my test does not pass.

tests.py

import os

from django.test import Client

from apps.price_list_excel_files.models import PriceListExcelFile


def upload_excel(user: str, passwd: str) -> tuple:
    client = Client()
    client.login(username=user, password=passwd)

    dir_path = os.path.dirname(os.path.realpath(__file__))
    with open(dir_path + '/mixed_case.xlsx', 'rb') as fp:
        response = client.post(
            '/api/price-list-excel-files/',
            {'file': fp},
            format='multipart'
        )
    return client, response


def test_mgmt_user_upload_excel(prepare_mgmt_users):
    client, response = upload_excel("John", "johnpassword")
    assert 201 == response.status_code
    assert 1 == PriceListExcelFile.objects.count()


# TODO: Fix this testcase
def test_mgmt_user_remove_excel(prepare_mgmt_users):
    client, response = upload_excel("John", "johnpassword")
    excel_id = response.data.get('id')
    url = '/api/price-list-excel-files/' + str(excel_id) + '/'
    res2 = client.delete(url, data={'format': 'json'})
    import pdb;
    pdb.set_trace()

    assert 0 == PriceListExcelFile.objects.count()

Here is my pdb console:

apps/price_list_excel_files/tests.py .
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> PDB set_trace (IO-capturing turned off) >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
> /Users/el/Code/siam-sbrand/portal/apps/price_list_excel_files/tests.py(37)test_mgmt_user_remove_excel()
-> assert 0 == PriceListExcelFile.objects.count()
(Pdb) list
 32         url = '/api/price-list-excel-files/' + str(excel_id) + '/'
 33         res2 = client.delete(url, data={'format': 'json'})
 34         import pdb;
 35         pdb.set_trace()
 36
 37  ->     assert 0 == PriceListExcelFile.objects.count()
[EOF]
(Pdb) res2
*** KeyError: 'content-type'
(Pdb) url
'/api/price-list-excel-files/2/'
(Pdb) res3 = client.delete(url)
(Pdb) res3
<Response status_code=404, "application/json">

Am I miss something?