Read the responses to the post below yours. Not a kata issue, it's your code what's wrong.

Everything works with python 3.4
but python 2 still have that issue

Seems like the new translation didn't go through even after approval so I just slapped the code into the kata directly.

It should be resolved now ;-)

There were some rounding errors in the reference solution.

I published a translation fork that should resolve the issue (and added support for py3).