Fix versioning script on Python 3.

support/buildbot/Versioning

@@ -20,6 +20,9 @@ sources = [
 
   # This is a hack, but we need some way to only run this script when HG changes.
   os.path.join(builder.sourcePath, '.hg', 'dirstate'),
+
+  # The script source is a dependency, of course...
+  argv[1]
 ]
 cmd_node, output_nodes = builder.AddCommand(
   inputs=sources,

support/buildbot/generate_headers.py

@@ -14,6 +14,8 @@ OutputFolder = os.path.normpath(argv[1])
 def get_hg_version():
   argv = ['hg', 'parent', '-R', SourceFolder]
   text = subprocess.check_output(argv)
+  if str != bytes:
+    text = str(text, 'utf-8')
   m = re.match('changeset:\s+(\d+):(.+)', text)
   if m == None:
     raise Exception('Could not determine repository version')