Follow-up to r3141, forgot to import `to_unicode` + better error message for timeline event provider failure
Follow-up to r3141, forgot to import `to_unicode` + better error message for timeline event provider failure

git-svn-id: f68c6b3b1dcd5d00a2560c384475aaef3bc99487@3157 af82e41b-90c4-0310-8c96-b1721e28e2e2

exocad/exotrac,dafrito/trac-mirror,exocad/exotrac,dokipen/trac,moreati/trac-gitsvn,dafrito/trac-mirror,exocad/exotrac,moreati/trac-gitsvn,exocad/exotrac,moreati/trac-gitsvn,dafrito/trac-mirror,moreati/trac-gitsvn,dokipen/trac,dafrito/trac-mirror,dokipen/trac