Guess file extension based on content-type. When downloading a file, and no path is supplied to store it, guess the file extension using mimetypes and the content-type header. Also supply a unit test for the HotLinkImageForm.

from django.apps import AppConfig


class PotdConfig(AppConfig):
    name = 'potd'
    verbose_name = 'Photo of the Day'
    label = 'potd'

    def ready(self):
        import potd.receivers