BTW if you're using the community package you could just use CALIBRE_PYTHON_PATH and CALIBRE_RESOURCES_PATH instead, see the contents of /usr/bin/calibre.
Also CALIBRE_EXTENSIONS_PATH if you're really interested in hacking the C extensions, but at that point I say just do like I do and install the calibre dependencies, but not calibre itself, and use `python2 setup.py develop` to install the source code. See
https://github.com/kovidgoyal/calibr...master/INSTALL
(Ironically I don't usually use the binary package I uploaded to [community].
)