Update tooling to use yapf for Python file formatting (issue #2171)

tools/yapf_util.py

@@ -0,0 +1,26 @@
+# Copyright (c) 2017 The Chromium Embedded Framework Authors. All rights
+# reserved. Use of this source code is governed by a BSD-style license that
+# can be found in the LICENSE file
+
+from exec_util import exec_cmd
+import os
+import sys
+
+# Script directory.
+script_dir = os.path.dirname(__file__)
+root_dir = os.path.join(script_dir, os.pardir)
+
+
+def yapf_format(file_name, file_contents):
+  # Reads .style.yapf in the root_dir when specifying contents via stdin.
+  result = exec_cmd("%s %s/yapf" % (sys.executable, script_dir), root_dir,
+                    file_contents)
+  if result['err'] != '':
+    print "yapf error: %s" % result['err']
+  if result['out'] != '':
+    output = result['out']
+    if sys.platform == 'win32':
+      # Convert to Unix line endings.
+      output = output.replace("\r", "")
+    return output
+  return None