gn.py dies with exception when it can't find buildtools/

gclient_utils.py

 # 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.
 
 """Generic utils."""
 
 import codecs
 import cStringIO
 import datetime
 import logging
@@ skipping 680 matching lines @@
   """Returns the full path to the buildtools directory.
   This is based on the root of the checkout containing the current directory."""
 
   # Overriding the build tools path by environment is highly unsupported and may
   # break without warning.  Do not rely on this for anything important.
   override = os.environ.get('CHROMIUM_BUILDTOOLS_PATH')
   if override is not None:
     return override
 
   primary_solution = GetPrimarySolutionPath()
+  if primary_solution is None:
+    return None
   buildtools_path = os.path.join(primary_solution, 'buildtools')
   if not os.path.exists(buildtools_path):
     # Buildtools may be in the gclient root.
     gclient_root = FindGclientRoot(os.getcwd())
     buildtools_path = os.path.join(gclient_root, 'buildtools')
   return buildtools_path
 
 
 def GetBuildtoolsPlatformBinaryPath():
   """Returns the full path to the binary directory for the current platform."""
@@ skipping 480 matching lines @@
 def DefaultIndexPackConfig(url=''):
   """Return reasonable default values for configuring git-index-pack.
 
   Experiments suggest that higher values for pack.threads don't improve
   performance."""
   cache_limit = DefaultDeltaBaseCacheLimit()
   result = ['-c', 'core.deltaBaseCacheLimit=%s' % cache_limit]
   if url in THREADED_INDEX_PACK_BLACKLIST:
     result.extend(['-c', 'pack.threads=1'])
   return result