Add a long-needed sanity check to cvs2svn:
Add a long-needed sanity check to cvs2svn:

* tools/cvs2svn/cvs2svn.py
  (convert): Error out if cvs repository does not exist.

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