pmaint sync fails to catch rsync exception when no network connection avail.

[djanderson]

pmaint sync from integration branch r3345 (and all versions in tree) produce a traceback when no network connection is available. This traceback was produced using default rsync method, other sync methods untested.

# pmaint sync
*** syncing '/usr/portage'...
Traceback (most recent call last):
  File "/home/dja/dev/pkgcore/bin/pmaint", line 24, in <module>
    commandline.main(subcommands)
  File "/home/dja/dev/pkgcore/pkgcore/util/commandline.py", line 432, in main
    exitstatus = main_func(options, out, err)
  File "/home/dja/dev/pkgcore/pkgcore/scripts/pmaint.py", line 78, in sync_main
    if not ops.sync():
  File "/home/dja/dev/pkgcore/pkgcore/interfaces/repo.py", line 436, in _cmd_enabled_sync
    return self._cmd_sync(self._default_observer(observer))
  File "/home/dja/dev/pkgcore/pkgcore/interfaces/repo.py", line 439, in _cmd_sync
    return self._get_syncer().sync()
  File "/home/dja/dev/pkgcore/pkgcore/sync/base.py", line 85, in sync
    return self._sync(verbosity, 1, **kwds)
  File "/home/dja/dev/pkgcore/pkgcore/sync/rsync.py", line 185, in _sync
    ret = rsync_syncer._sync(self, verbosity, output_fd)
  File "/home/dja/dev/pkgcore/pkgcore/sync/rsync.py", line 122, in _sync
    for count, ip in zip(xrange(self.retries), self._get_ips()):
  File "/home/dja/dev/pkgcore/pkgcore/sync/rsync.py", line 101, in _get_ips
    raise base.syncer_exception(self.hostname, af_fam, str(e))
pkgcore.sync.base.syncer_exception: ('rsync.gentoo.org', 2, '[Errno -3] Temporary failure in name resolution')

[ferringb]

rev 3837 of my branch fixes this...