stack/erp5: patch RestrictedPython to compile with print_function

Every restricted python code on python2 will be compiled as if it had
`from __future__ import print_function`, to ease transition away from
python2.

To update project code, 2to3 from python2.7 seems to do a good job.
Invoking like from the root of a repository rewrite all scripts:

    2to3  --write --nobackups --no-diffs --fix=print .