Please describe the problem:
I'm having trouble setting a window title (window.set_title('')) when the
title-string includes a special character, specifically a specially modified
character called macron (e.g.: ā).
windows then wouldn't want to show the title at all anymore. (i was told it is
showing on linux though.)
maybe this is a bug? or is there a way to solve this problem?

Steps to reproduce:
1. create a gtk.window 
2. window.set_title('lālala')



Actual results:
title is not shown anymore at all

Expected results:
title-string should be displayed in window

Does this happen every time?
yes

Other information:
this does not happen with all diacritical letters. e.g. circumflexe (â) and
umlauts / tremas (ä) are correctly shown.