Create output dir in logcat printer if it doesn't exist.

build/android/adb_logcat_printer.py

 #!/usr/bin/env python
 #
 # Copyright (c) 2012 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.
 
 """Shutdown adb_logcat_monitor and print accumulated logs.
 
 To test, call './adb_logcat_printer.py <base_dir>' where
 <base_dir> contains 'adb logcat -v threadtime' files named as
@@ skipping 141 matching lines @@
 
 
 def main(argv):
   parser = optparse.OptionParser(usage='Usage: %prog [options] <log dir>')
   parser.add_option('--output-path',
                     help='Output file path (if unspecified, prints to stdout)')
   options, args = parser.parse_args(argv)
   if len(args) != 1:
     parser.error('Wrong number of unparsed args')
   base_dir = args[0]
-  if options.output_path:
-    output_file = open(options.output_path, 'w')
-  else:
-    output_file = sys.stdout
 
   log_stringio = cStringIO.StringIO()
   logger = logging.getLogger('LogcatPrinter')
   logger.setLevel(LOG_LEVEL)
   sh = logging.StreamHandler(log_stringio)
   sh.setFormatter(logging.Formatter('%(asctime)-2s %(levelname)-8s'
                                     ' %(message)s'))
   logger.addHandler(sh)
 
+  if options.output_path:
+    if not os.path.exists(os.path.dirname(options.output_path)):
+      logger.warning('Output dir %s doesn\'t exist. Creating it.',
+                      os.path.dirname(options.output_path))
+      os.makedirs(os.path.dirname(options.output_path))
+    output_file = open(options.output_path, 'w')
+    logger.info('Dumping logcat to local file %s. If running in a build, '
+                'this file will likely will be uploaded to google storage '
+                'in a proceeding step. It can be downloaded from there.',

[jbudorick, 2016/03/25 17:25:19]

nit: s/proceeding/later/

+                options.output_path)
+  else:
+    output_file = sys.stdout
+
   try:
     # Wait at least 5 seconds after base_dir is created before printing.
     #
     # The idea is that 'adb logcat > file' output consists of 2 phases:
     #  1 Dump all the saved logs to the file
     #  2 Stream log messages as they are generated
     #
     # We want to give enough time for phase 1 to complete.  There's no
     # good method to tell how long to wait, but it usually only takes a
     # second.  On most bots, this code path won't occur at all, since
@@ skipping 19 matching lines @@
   except:
     logger.exception('Unexpected exception')
 
   logger.info('Done.')
   sh.flush()
   output_file.write('\nLogcat Printer Event Log\n')
   output_file.write(log_stringio.getvalue())
 
 if __name__ == '__main__':
   sys.exit(main(sys.argv[1:]))