from django.contrib.admin.forms import AdminAuthenticationForm

from django.contrib.admin.helpers import ActionForm

from django.core.exceptions import ValidationError

class CustomAdminAuthenticationForm(AdminAuthenticationForm):

    class Media:

        css = {"all": ("path/to/media.css",)}

    def clean_username(self):

        username = self.cleaned_data.get("username")

        if username == "customform":

            raise ValidationError("custom form error")

        return username

class MediaActionForm(ActionForm):

    class Media:

        js = ["path/to/media.js"]