Make Swarming bot keep 5%+250MB of the disk free.

appengine/swarming/swarming_bot/bot_code/bot_main_test.py

 #!/usr/bin/env python
 # Copyright 2013 The LUCI Authors. All rights reserved.
 # Use of this source code is governed under the Apache License, Version 2.0
 # that can be found in the LICENSE file.
 
 import json
 import logging
 import os
 import sys
 import tempfile
@@ skipping 480 matching lines @@
             self.root_dir, 'w', 'task_runner_out.json')
         expected = [
           sys.executable, bot_main.THIS_FILE, 'task_runner',
           '--swarming-server', url,
           '--in-file',
           os.path.join(self.root_dir, 'w', 'task_runner_in.json'),
           '--out-file', self2._out_file,
           '--cost-usd-hour', '3600.0', '--start', '100.0',
           '--min-free-space',
           str(int(
-            (os_utilities.get_min_free_space(bot_main.THIS_FILE) + 250.) *
-            1024 * 1024)),
+            os_utilities.get_desired_free_space(bot_main.THIS_FILE)*1024*1024)),
         ]
         self.assertEqual(cmd[15], '--bot-file')
         self.assertTrue(cmd[16].endswith('.json'))
         del cmd[15:17]
         if expected_auth_params_json:
           auth_params_file = os.path.join(
               self.root_dir, 'w', 'bot_auth_params.json')
           with open(auth_params_file, 'rb') as f:
             actual_auth_params = json.load(f)
           self.assertEqual(expected_auth_params_json, actual_auth_params)
@@ skipping 206 matching lines @@
     self.assertEqual(0, bot_main.main([]))
 
 
 if __name__ == '__main__':
   fix_encoding.fix_encoding()
   if '-v' in sys.argv:
     TestBotMain.maxDiff = None
   logging.basicConfig(
       level=logging.DEBUG if '-v' in sys.argv else logging.CRITICAL)
   unittest.main()