I would like to give some feedback about ...

From: http://www.checkio.org/mission/boolean-algebra/solve/

HTTP_USER_AGENT:

Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:33.0) Gecko/20100101 Firefox/33.0

on one of the tests the following assertion is attempted: boolean(0, 0, u"implication")

which is malformed.