Handle the case where a shard crashed and did not generate an xml file.

sharding_supervisor.py

 #!/usr/bin/env python
 # Copyright (c) 2011 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 """Shards a given test suite and runs the shards in parallel.
 
 ShardingSupervisor is called to process the command line options and creates
 the specified number of worker threads. These threads then run each shard of
 the test in a separate process and report on the results. When all the shards
@@ skipping 85 matching lines @@
     return
 
   args.remove('--gtest_output=' + current_value)
   return args
 
 
 def AppendToXML(final_xml, generic_path, shard):
   """Combine the shard xml file with the final xml file."""
 
   path = generic_path + str(shard)
-  with open(path) as shard_xml_file:
-    shard_xml = minidom.parse(shard_xml_file)
+
+  try:
+    with open(path) as shard_xml_file:
+      shard_xml = minidom.parse(shard_xml_file)
+  except IOError:
+    # If the shard crashed, gtest will not have generated an xml file.
+    return final_xml
 
   if not final_xml:
     # Out final xml is empty, let's prepopulate it with the first one we see.
     return shard_xml
 
   shard_node = shard_xml.documentElement
   final_node = final_xml.documentElement
 
   testcases = shard_node.getElementsByTagName('testcase')
   final_testcases = final_node.getElementsByTagName('testcase')
@@ skipping 244 matching lines @@
 
     # All the shards are done.  Merge all the XML files and generate the
     # main one.
     output_arg = GetGTestOutput(self.gtest_args)
     if output_arg:
       xml, xml_path = output_arg.split(':', 1)
       assert(xml == 'xml')
       final_xml = None
       for i in range(start_point, start_point + self.num_shards_to_run):
         final_xml = AppendToXML(final_xml, xml_path, i)
-      with open(xml_path, 'w') as final_file:
-        final_xml.writexml(final_file)
+
+      if final_xml:
+        with open(xml_path, 'w') as final_file:
+          final_xml.writexml(final_file)
 
     num_failed = len(self.failed_shards)
     if num_failed > 0:
       self.failed_shards.sort()
       self.WriteText(sys.stdout,
                      "\nFAILED SHARDS: %s\n" % str(self.failed_shards),
                      "\x1b[1;5;31m")
     else:
       self.WriteText(sys.stdout, "\nALL SHARDS PASSED!\n", "\x1b[1;5;32m")
     self.PrintSummary(self.failed_tests)
@@ skipping 236 matching lines @@
   # shard and run the whole test
   ss = ShardingSupervisor(
       args[0], num_shards_to_run, num_runs, options.color,
       options.original_order, options.prefix, options.retry_percent,
       options.timeout, options.total_slaves, options.slave_index, gtest_args)
   return ss.ShardTest()
 
 
 if __name__ == "__main__":
   sys.exit(main())