'Identify client using plaintext password.
(typ, [data]) = <instance>.login(user, password)
NB: \'password\' will be quoted.'

def login(self, user, password):

    (typ, dat) = self._simple_command('LOGIN', user, self._quote(password))
    if (typ != 'OK'):
        raise self.error(dat[(-1)])
    self.state = 'AUTH'
    return (typ, dat)
