[FIX] wiki: Raise not found exception if page not found

git-svn-id: file:///var/local/code.tiki.org/tikisvn/branches/12.x@50350 b456876b-0849-0410-b77d-98878d47e9d5
[FIX] services: Use message set in constructor

git-svn-id: file:///var/local/code.tiki.org/tikisvn/branches/12.x@50351 b456876b-0849-0410-b77d-98878d47e9d5