Dear Rudy and Thomas,
I has a similar problem with tornado, toro, and jsonrpclib getting loaded into Python 3.5. I got around this problem by changing the following line in install-evok.sh file:
"pip install tornado toro jsonrpclib"
"/usr/bin/pip-2.7 install tornado toro jsonrpclib"
It forced the install to Python 2.7 libraries
I updated build-essentials and python-dev for 2.7 (and all other versions) first:
"sudo apt-get install build-essential python-dev"