Make the homedir check a bit simpler.

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 42 matching lines @@
 # permissions. It'd be easier if we could default to $USERNAME, but $USERNAME
 # is "root" here because we get called through sudo.
 #
 # We need to set this before importing any portage modules, because portage
 # looks up "PORTAGE_USERNAME" at import time.
 #
 # NOTE: .bashrc sets PORTAGE_USERNAME = $USERNAME, so most people won't
 # encounter this case unless they have an old chroot or blow away the
 # environment by running sudo without the -E specifier.
 if "PORTAGE_USERNAME" not in os.environ:
-  homedir = os.environ["HOME"]
-  if homedir.startswith("/home/"):
-    os.environ["PORTAGE_USERNAME"] = homedir.split("/")[2]
+  homedir = os.environ.get("HOME")
+  if homedir:
+    os.environ["PORTAGE_USERNAME"] = os.path.basename(homedir)
 
 # Portage doesn't expose dependency trees in its public API, so we have to
 # make use of some private APIs here. These modules are found under
 # /usr/lib/portage/pym/.
 #
 # TODO(davidjames): Update Portage to expose public APIs for these features.
 from _emerge.actions import adjust_configs
 from _emerge.actions import load_emerge_config
 from _emerge.create_depgraph_params import create_depgraph_params
 from _emerge.depgraph import backtrack_depgraph
@@ skipping 942 matching lines @@
 
   It expects package identifiers to be passed to it via task_queue. When
   the package is merged, it pushes (target, retval, outputstr) into the
   done_queue.
   """
 
   settings, trees, mtimedb = emerge.settings, emerge.trees, emerge.mtimedb
   opts, spinner = emerge.opts, emerge.spinner
   opts["--nodeps"] = True
   while True:
+    # Wait for a new item to show up on the queue. This is a blocking wait,
+    # so if there's nothing to do, we just sit here.
     target = task_queue.get()
     print "Emerging", target
     db_pkg = package_db[target]
     db_pkg.root_config = emerge.root_config
     install_list = [db_pkg]
     output = tempfile.TemporaryFile()
     outputstr = ""
     if "--pretend" in opts:
       retval = 0
     else:
@@ skipping 219 matching lines @@
       for db_pkg in final_db.match_pkgs(pkg):
         print "Adding %s to world" % db_pkg.cp
         new_world_pkgs.append(db_pkg.cp)
     if new_world_pkgs:
       world_set.update(new_world_pkgs)
 
   print "Done"
 
 if __name__ == "__main__":
   main()