On recent Fedora 26 install, I encountered an error (shown below) attempting to install sabnzbd.
I found the wiki at https://sabnzbd.org/wiki/installation/install-fedora-centos-rhel. From this wiki, I went to the nuxref repository at http://nuxref.com/nuxref-repository/ and clicked on the following link:
Fedora 26: nuxref-release-1.0.0-4.fc26.nuxref.noarch.rpm
Downloading the rpm, I selected the default action of "software install", which apparently installed the rpm. Then I opened a bash terminal and executed
sudo dnf install sabnzbd. This resulted in the following error message:
Problem: conflicting requests - nothing provides python-sabyenc >= 3.0.2 needed by sabnzbd-2:2.2.1-1.fc26.nuxref.noarch