Upgraded Kubuntu to 15.10. When running Muon-discover (or another packet-manager, tried Synaptic), it exits with this error (via terminal):
muon-updater: symbol lookup error: /usr/lib/x86_64-linux-gnu/libQApt.so.3: undefined symbol: _ZN6Xapian8DatabaseC1ERKNSt7__cxx1112basic_stringIcSt11char_traitsIcESaIcEEE