parallel_emerge: catch 404 errors when getting packages

parallel_emerge

 #!/usr/bin/python2.6
 # Copyright (c) 2010 The Chromium OS Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 """Program to run emerge in parallel, for significant speedup.
 
 Usage:
  ./parallel_emerge [--board=BOARD] [--workon=PKGS] [--no-workon-deps]
                    [emerge args] package"
@@ skipping 795 matching lines @@
       Returns:
         A dict mapping package identifiers to modification times.
       """
 
       if not binhost_url:
         return {}
 
       url = binhost_url + "/Packages"
 
       prebuilt_pkgs = {}
-      f = urllib2.urlopen(url)
+      try:
+        f = urllib2.urlopen(url)
+      except urllib2.HTTPError as e:
+        if e.code == 404:
+          return {}
+        else:
+          raise
       for line in f:
         if line.startswith("CPV: "):
           pkg = line.replace("CPV: ", "").rstrip()
         elif line.startswith("MTIME: "):
           prebuilt_pkgs[pkg] = int(line[:-1].replace("MTIME: ", ""))
       f.close()
 
       return prebuilt_pkgs
 
     def LocalPackageDatabase():
@@ skipping 496 matching lines @@
       world_set.update(new_world_pkgs)
 
   # Update environment (library cache, symlinks, etc.)
   if deps.board and "--pretend" not in emerge.opts:
     portage.env_update()
 
   print "Done"
 
 if __name__ == "__main__":
   main()