'Evaluate text and return (obj, valid)
where *obj* is the object represented by *text*
and *valid* is True if object evaluation did not raise any exception'

def _eval(self, text):

    assert is_text_string(text)
    ns = self._get_current_namespace(with_magics=True)
    try:
        return (eval(text, ns), True)
    except:
        return (None, False)
