Remove PYTHONPATH requirement to execute run_slave.py.

slave/buildbot.tac

 # -*- python -*-
 # ex: set syntax=python:
 
 # Copyright (c) 2010 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.
 
 # Chrome Buildbot slave configuration
 
 import os
@@ skipping 29 matching lines @@
     import socket
     slavename = socket.getfqdn().split('.')[0].lower()
 
 if password is None:
     msg = '*** No password configured in %s.\n' % repr(__file__)
     sys.stderr.write(msg)
     sys.exit(1)
 
 if ActiveMaster is None:
   ActiveMaster = slave_utils.GetActiveMasterConfig()
+  if not ActiveMaster:
+    sys.stderr.write(
+        '\nCouldn\'t determine the slave type automatically.\n'
+        'Please update buildbot.tac to set ActiveMaster and slavename to the\n'
+        'relevant values.\n\n')
+    sys.exit(1)
 
 if host is None:
     host = ActiveMaster.master_host
 
 if port is None:
     port = ActiveMaster.slave_port
 
 if basedir is None:
     dir, _file = os.path.split(__file__)
     basedir = os.path.abspath(dir)
 
 
 application = service.Application('buildslave')
 s = BuildSlave(host, port, slavename, password, basedir, keepalive, usepty,
                umask=umask)
 s.setServiceParent(application)