schemePy with the holodeck webfrontend (app.py)requires python version 3.4 to be installed. It does not work with python2.7 or below!
$ python3 --version
Python 3.4.1
Sadly, Debian based software repositories currently only provide binaries for python 3.3. This is enough to run the schemepy repl (repl.py).
If you want to use the webfrontend as well, please install python3.4 from the offical python homepage1. Afterwards you need to install the flask framework for python3:
If you are using an virtualenv
python3 -m pip install flask
otherwise:
sudo python3 -m pip install flask