Code review comment for lp:~mathias-porten/scratch/fix-1467148

I get this error when I launch scratch with your code:

[_LOG_LEVEL_WARN 18:29:57.707047] [Gtk] Failed to set text from markup due to error parsing markup: Unknown tag 'h4' on line 1 char 21

Here is what is done for instance in Pantheon Files:
label.get_style_context ().add_class ("h4");

Please test your merge request at least once before asking for a review ;)