Proper POST file upload (load testing with Locust)

Well, I found the solution and I hope it will be useful for someone:

Here was described how Django handles file: How to send a "multipart/form-data" with requests in python?

And recipe is to define 'files' param in post function:

    r = self.client.post("/submit/", data={
        'csrfmiddlewaretoken': csrftoken,
        'password': smart_str(u'wkefjgui'),
        'payload': smart_str(u'kjsdgfljdsh'),
        'commit': smart_str(u'Вкрапить / Embed'),
         }, files={'docfile': attach})

handle multipart file

 def _get_image_part(self, file_path, file_content_type='image/jpeg'):
        import os
        file_name = os.path.basename(file_path)
        file_content = open(file_path, 'rb')
        return file_name, file_content, file_content_type

multipart test case

class OpenDeviceFrontApi(TaskSet):

    @task(2)
    def rec_log_upload(self):
        payload = {
            "device_key": device_key
        }
        files = {
            "scene_img": self._get_image_part("data/face/rec1.jpg"),
            "face_img": self._get_image_part("data/face/rec2.jpg")
        }
        r = self.client.post("/log/rec_log_upload", data=payload, files=files, verify=False)
        assert r.status_code == 200
        rData = json.loads(r.text, encoding="utf-8")