See e-mail verification method

def EMAIL_VERIFICATION(self):
        """
        See e-mail verification method
        """
        ret = self._setting("EMAIL_VERIFICATION",
                            self.EmailVerificationMethod.OPTIONAL)
        # Deal with legacy (boolean based) setting
        if ret is True:
            ret = self.EmailVerificationMethod.MANDATORY
        elif ret is False:
            ret = self.EmailVerificationMethod.OPTIONAL
        return ret