Check the existence and executability of scm commands

gclient_scm.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.
 
 """Gclient-specific SCM-specific operations."""
 
 import logging
 import os
 import posixpath
 import re
@@ skipping 67 matching lines @@
 
 def CreateSCM(url, root_dir=None, relpath=None):
   SCM_MAP = {
     'svn' : SVNWrapper,
     'git' : GitWrapper,
   }
 
   scm_name = GetScmName(url)
   if not scm_name in SCM_MAP:
     raise gclient_utils.Error('No SCM found for url %s' % url)
+  if not gclient_utils.FindCommandExecutable(scm_name):
+    raise gclient_utils.Error('%s command not found' % scm_name)
   return SCM_MAP[scm_name](url, root_dir, relpath)
 
 
 # SCMWrapper base class
 
 class SCMWrapper(object):
   """Add necessary glue between all the supported SCM.
 
   This is the abstraction layer to bind to different SCM.
   """
@@ skipping 1031 matching lines @@
       new_command.append('--force')
       if command[0] != 'checkout' and scm.SVN.AssertVersion('1.6')[0]:
         new_command.extend(('--accept', 'theirs-conflict'))
     elif options.manually_grab_svn_rev:
       new_command.append('--force')
       if command[0] != 'checkout' and scm.SVN.AssertVersion('1.6')[0]:
         new_command.extend(('--accept', 'postpone'))
     elif command[0] != 'checkout' and scm.SVN.AssertVersion('1.6')[0]:
       new_command.extend(('--accept', 'postpone'))
     return new_command