Gtk.Builder.add_from_string() breaks when used with non-ascii chars

To be exact there have to be more than 15 non ascii chars in the string for it to break

Its only my first guess that this is a pygobject problem, i just think this would have been catched earlier if it is a GTK problem

Gtk: 3.24.0 pygobject: 3.30.0

Example:

import gi
gi.require_version('Gtk', '3.0')
from gi.repository import Gtk
 
xml = '''
<interface>
  <menu id="appmenu">
    <section>
      <item>
        <attribute name="label">%s</attribute>
      </item>
    </section>
  </menu>
</interface>
'''
 
a = '¶¶¶¶¶¶¶¶¶¶¶¶¶¶¶'
print(len(a))
 
int_ = [ord(char) for char in a]
print(int_)
 
xml = xml % a
 
builder = Gtk.Builder()
builder.add_from_string(xml)