Don't terminate with a backtrace when a 404 is encountered. This

Don't terminate with a backtrace when a 404 is encountered.  This
try/catch makes it just slighlty better, but not really as nice as it
should be (lots of misalignment, redundant/double data and missing data):

% emerge -Kgp gawk

These are the packages that would be merged, in order:

Calculating dependencies -

Fetching binary packages info...
!!! Unable to get listing: 404 Server did not respond successfully (404: Not Found)
  -- DONE!
                                                                              ... done!

svn path=/main/branches/prefix/; revision=8463