Fixes and add smoke test: hard timeout on isolated task.

appengine/swarming/tools/start_bot.py

 #!/usr/bin/env python
 # Copyright 2015 The Swarming Authors. All rights reserved.
 # Use of this source code is governed by the Apache v2.0 license that can be
 # found in the LICENSE file.
 
 """Starts a local bot to connect to a local server."""
 
 import glob
 import os
 import signal
@@ skipping 35 matching lines @@
     if self._redirect:
       logs = os.path.join(self._tmpdir, 'logs')
       if not os.path.isdir(logs):
         os.mkdir(logs)
       with open(os.path.join(logs, 'bot_stdout.log'), 'wb') as f:
         self._proc = subprocess.Popen(
             cmd, cwd=self._tmpdir, stdout=f, env=env, stderr=f, **kwargs)
     else:
       self._proc = subprocess.Popen(cmd, cwd=self._tmpdir, env=env, **kwargs)
 
-  def stop(self):
+  def stop(self, leak):
     """Stops the local Swarming bot. Returns the process exit code."""
     if not self._proc:
       return None
     if self._proc.poll() is None:
       try:
         self._proc.send_signal(signal.SIGTERM)
         # TODO(maruel): SIGKILL after N seconds.
         self._proc.wait()
       except OSError:
         pass
     exit_code = self._proc.returncode
     if self._tmpdir:
       for i in sorted(glob.glob(os.path.join(self._tmpdir, 'logs', '*.log'))):
         self._read_log(i)
-      try:
-        shutil.rmtree(self._tmpdir)
-      except OSError:
-        print >> sys.stderr, 'Leaking %s' % self._tmpdir
+      if not leak:
+        try:
+          shutil.rmtree(self._tmpdir)
+        except OSError:
+          print >> sys.stderr, 'Leaking %s' % self._tmpdir
       self._tmpdir = None
     self._proc = None
     return exit_code
 
   def wait(self):
     """Waits for the process to normally exit."""
     self._proc.wait()
 
   def kill(self):
     """Kills the child forcibly."""
@@ skipping 27 matching lines @@
     print >> sys.stderr, 'Specify url to Swarming server'
     return 1
   bot = LocalBot(sys.argv[1], False)
   try:
     bot.start()
     bot.wait()
     bot.dump_log()
   except KeyboardInterrupt:
     print >> sys.stderr, '<Ctrl-C> received; stopping bot'
   finally:
-    exit_code = bot.stop()
+    exit_code = bot.stop(False)
   return exit_code
 
 
 if __name__ == '__main__':
   sys.exit(main())