radicale has a serious py2/py3 mismatch in F23. The python module is now python3, but the radicale-httpd package depends on mod_wsgi - which is the *python 2* wsgi. It tries to run /usr/share/radicale/radicale.wsgi under python2, and it obviously fails when it tries to do 'import radicale', because there is no py2 radicale any more. If you install python3-mod_wsgi and rpm -e --nodeps mod_wsgi it gets further, but still fails to work on a subsequent problem, I'll file that separately. radicale-httpd should require python3-mod_wsgi not mod_wsgi.
I'm sorry, I forgot to test that subpackage. I'm going to push an update right now.
radicale-1.0.1-3.fc23 has been submitted as an update to Fedora 23. https://bodhi.fedoraproject.org/updates/FEDORA-2015-c10347d45f
radicale-1.0.1-3.fc23 has been pushed to the Fedora 23 testing repository. If problems still persist, please make note of it in this bug report. If you want to test the update, you can install it with $ su -c 'dnf --enablerepo=updates-testing update radicale' You can provide feedback for this update here: https://bodhi.fedoraproject.org/updates/FEDORA-2015-c10347d45f
radicale-1.0.1-3.fc23 has been pushed to the Fedora 23 stable repository. If problems still persist, please make note of it in this bug report.