Efforts to port calibre to python 3 are ongoing. calibre can be run
using python3 under Linux. To do so, install python 3, checkout calibre
from source with

    git clone git@github.com:kovidgoyal/calibre.git && cd calibre

Then, setup calibre to run under python2, with:

    python2 setup.py bootstrap

Check that calibre works, with:

    python2 run-local calibre

Now build the calibre C extensions for python 3 with:

    CALIBRE_PY3_PORT=1 python3 setup.py build

You should now be able to run the calibre test suite using:

    CALIBRE_PY3_PORT=1 python3 setup.py test

And run calibre itself (which may not work) with:

    python3 run-local calibre


For the status of the port, and discussion of its design, see
https://github.com/kovidgoyal/calibre/pull/870