Add an alternate default boto file for bootstrapping source.

download_from_google_storage.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.
 
 """Download files from Google Storage based on SHA1 sums."""
 
 
 import hashlib
 import optparse
@@ skipping 24 matching lines @@
 class Gsutil(object):
   """Call gsutil with some predefined settings.  This is a convenience object,
   and is also immutable."""
   def __init__(self, path, boto_path, timeout=None):
     if not os.path.exists(path):
       raise FileNotFoundError('GSUtil not found in %s' % path)
     self.path = path
     self.timeout = timeout
     self.boto_path = boto_path
 
-  def call(self, *args):
+  def get_sub_env(self):
     env = os.environ.copy()
     if self.boto_path:
       env['AWS_CREDENTIAL_FILE'] = self.boto_path
+    else:
+      custompath = env.get('AWS_CREDENTIAL_FILE', '~/.boto') + '.depot_tools'
+      custompath = os.path.expanduser(custompath)
+      if os.path.exists(custompath):
+        env['AWS_CREDENTIAL_FILE'] = custompath
+
+    return env
+
+  def call(self, *args):
     return subprocess2.call((sys.executable, self.path) + args,
-                            env=env,
+                            env=self.get_sub_env(),
                             timeout=self.timeout)
 
   def check_call(self, *args):
-    env = os.environ.copy()
-    if self.boto_path:
-      env['AWS_CREDENTIAL_FILE'] = self.boto_path
     ((out, err), code) = subprocess2.communicate(
         (sys.executable, self.path) + args,
         stdout=subprocess2.PIPE,
         stderr=subprocess2.PIPE,
-        env=env,
+        env=self.get_sub_env(),
         timeout=self.timeout)
 
     # Parse output.
     status_code_match = re.search('status=([0-9]+)', err)
     if status_code_match:
       return (int(status_code_match.group(1)), out, err)
     if ('You are attempting to access protected data with '
           'no configured credentials.' in err):
       return (403, out, err)
     if 'No such object' in err:
@@ skipping 257 matching lines @@
     return code
 
   return download_from_google_storage(
       input_filename, base_url, gsutil, options.num_threads, options.directory,
       options.recursive, options.force, options.output, options.ignore_errors,
       options.sha1_file)
 
 
 if __name__ == '__main__':
   sys.exit(main(sys.argv))