In registration menu, checking email already exist or not!

forms.py

def clean_email(self):
        email = self.cleaned_data.get('email')
        username = self.cleaned_data.get('username')
        if email and User.objects.filter(
                email=email).exclude(username=username).count():
            raise forms.ValidationError(
                "A user with that email already exists")
        return email