Merge r1643409 from trunk:

 * r1643409
   Correctly reject requests with missing repos paths.
   Justification:
     These requests aren't valid and should result in an error.
   Votes:
     +1: breser, philip, kotkov


git-svn-id: https://svn.apache.org/repos/asf/subversion/branches/1.8.x@1643454 13f79535-47bb-0310-9956-ffa450edef68