Improve error reporting.
Improve error reporting.

* subversion/tests/cmdline/svntest/tree.py
  (detect_conflict_files): Improve error message text/formatting, and
   include the message in the exception thrown by the function.

jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion