build: Add Python 3 support (see issue #2856)

tools/make_gypi_file.py

@@ -2,6 +2,7 @@
 # reserved. Use of this source code is governed by a BSD-style license that
 # can be found in the LICENSE file.
 
+from __future__ import absolute_import
 from cef_parser import *
 
 
@@ -96,7 +97,7 @@ if __name__ == "__main__":
 
   # verify that the correct number of command-line arguments are provided
   if len(sys.argv) < 2:
-    sys.stderr.write('Usage: ' + sys.argv[0] + ' <infile>')
+    sys.stderr.write('Usage: ' + sys.argv[0] + ' <infile>\n')
     sys.exit()
 
   # create the header object