Why does Email(not_empty=True) accept empty values?

Hello, everyone.

I don't understand why I get this:
> >>> validator = EmailValidator()
> >>> print validator.to_python('')
> None

being EmailValidator defined as:
====-start-=====
class EmailValidator(FancyValidator):
    
    def __init__(self, not_empty=True, resolve_domain=False, max=255,
                 **kwargs):
        super(EmailValidator, self).__init__(**kwargs)
        self.length_validator = MaxLength(max)
        self.email_validator = Email(not_empty=not_empty, strip=True,
                                     resolve_domain=resolve_domain)
    
    def validate_python(self, value, state):
        try:
            self.length_validator.to_python(value, state)
            return self.email_validator.to_python(value, state)
        except Invalid, msg:
            raise InvalidEmailError(msg, value, state)
=====-end-=====

Shouldn't validate_python() raise an exception if it receives an empty string?

Thanks in advance.
-- 
Gustavo Narea.
http://gustavonarea.net/

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