Xapdina/python-project-52

from django.contrib.auth import get_user_model
from django.contrib.auth.forms import UserCreationForm


def clean_username(self):
    username = self.cleaned_data.get('username')
    if self._meta.model.objects.exclude(pk=self.instance.pk). \
            filter(username__iexact=username).exists():
        self.add_error(
            'username',
            self.instance.unique_error_message(
                self._meta.model, ['username']
            )
        )

    return username


class CustomUserCreationForm(UserCreationForm):
    class Meta:
        model = get_user_model()
        fields = [
            'first_name',
            'last_name',
            'username',
        ]