This CL updates the parallel job library in the au test harness to be more robust.

ctest/ctest.py

 #!/usr/bin/python
 #
 # 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.
 
 """Wrapper for tests that are run on builders."""
 
 import fileinput
 import optparse
@@ skipping 265 matching lines @@
   base_image = None
   if zip_url:
     GrabZipAndExtractImage(zip_url, download_folder, _IMAGE_TO_EXTRACT)
     base_image = os.path.join(download_folder, _IMAGE_TO_EXTRACT)
   else:
     base_image = target_image
 
   update_engine_path = os.path.join(crosutils_root, '..', 'platform',
                                     'update_engine')
 
-  private_key_path = os.path.join(update_engine_path, 'unittest_key.pem')
-  public_key_path = GeneratePublicKey(private_key_path)
+  if clean:
+    private_key_path = os.path.join(update_engine_path, 'unittest_key.pem')
+    public_key_path = GeneratePublicKey(private_key_path)
 
   cmd = ['bin/cros_au_test_harness',
          '--base_image=%s' % base_image,
          '--target_image=%s' % target_image,
          '--board=%s' % board,
          '--type=%s' % type,
          '--remote=%s' % remote,
-         '--private_key=%s' % private_key_path,
-         '--public_key=%s' % public_key_path,
          ]
   if test_results_root: cmd.append('--test_results_root=%s' % test_results_root)
   if no_graphics: cmd.append('--no_graphics')
-  if clean: cmd.append('--clean')
+  # Using keys is only compatible with clean.
+  if clean:
+    cmd.append('--clean')
+    cmd.append('--private_key=%s' % private_key_path)
+    cmd.append('--public_key=%s' % public_key_path)
 
   cros_lib.RunCommand(cmd, cwd=crosutils_root)
 
 
 def main():
   parser = optparse.OptionParser()
   parser.add_option('-b', '--board',
                     help='board for the image to compare against.')
   parser.add_option('-c', '--channel',
                     help='channel for the image to compare against.')
@@ skipping 21 matching lines @@
   if not options.zipbase: parser.error('Need zip url base to get images.')
 
   RunAUTestHarness(options.board, options.channel, options.zipbase,
                    options.no_graphics, options.type, options.remote,
                    not options.cache, options.test_results_root)
 
 
 if __name__ == '__main__':
   main()