handle unknown recipes in 'fetch'.

fetch.py

 #!/usr/bin/env python
 # Copyright (c) 2013 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.
 
 """
 Tool to perform checkouts in one easy command line!
 
 Usage:
   fetch <recipe> [--property=value [--property2=value2 ...]]
@@ skipping 157 matching lines @@
 
   recipe = argv[1]
   props = argv[2:]
   return recipe, props
 
 
 def run_recipe_fetch(recipe, props, aliased=False):
   """Invoke a recipe's fetch method with the passed-through args
   and return its json output as a python object."""
   recipe_path = os.path.abspath(os.path.join(SCRIPT_PATH, 'recipes', recipe))
+  if not os.path.exists(recipe_path):
+    print "Could not find a recipe for %s" % recipe
+    sys.exit(1)
+
   cmd = [sys.executable, recipe_path + '.py', 'fetch'] + props
   result = subprocess.Popen(cmd, stdout=subprocess.PIPE).communicate()[0]
+
   spec = json.loads(result)
   if 'alias' in spec:
     assert not aliased
     return run_recipe_fetch(
         spec['alias']['recipe'], spec['alias']['props'] + props, aliased=True)
   cmd = [sys.executable, recipe_path + '.py', 'root']
   result = subprocess.Popen(cmd, stdout=subprocess.PIPE).communicate()[0]
   root = json.loads(result)
   return spec, root
 
@@ skipping 22 matching lines @@
 
 
 def main():
   recipe, props = handle_args(sys.argv)
   spec, root = run_recipe_fetch(recipe, props)
   return run(spec, root)
 
 
 if __name__ == '__main__':
   sys.exit(main())