Waiting for release of python lib. We can rebuild main script image on Monday so it gets pushed on Tuesday.

@zhebr Found the reason why it fails. And it was not due to this PR.
In python 2.7 we use this line fails: from Tkinter import _splitdict
and it is used in newer version of future==0.16.0 here:
https://github.com/PythonCharmers/python-future/blob/master/src/tkinter/__init__.py#L7

For now fixed it by adding explicit future==0.15.2 to reqs, but possibly better solution would be to update python2.7 (don't have this issue in 2.7.12, image uses 2.7.6)