[Fixed]-Django. Best way to have unique email in User model?

You are on the right track, the only thing that doesn’t look right is that you shouldn’t call clean method manually like this:

# These are not needed in your view method
username = form.clean_username()
email = form.clean_email()
password = form.clean_password2()

They are already called by form.is_valid(). See this SO question for details.