Workaround issue with gtk3 translation on windows.

Windows with python3 and Gtk3/pygi has this really nasty bug that translations
are actually working, but somehow the enconding is messed up by Gtk. This might
be fixed in newer versions of Gtk/pygi, but currently, we are stuck with 3.24
on Windows.

The idea of the workaround here is to parse the glade xml, and translate in
python all translatable strings, dump the xml on a temp file and then
load the interface from this tempfile. Works like a charm

Other references from a user with the same issue
https://stackoverflow.com/questions/32037573/
https://sourceforge.net/p/pygobjectwin32/tickets/22/
https://bugzilla.gnome.org/show_bug.cgi?id=753991

And the source of the workaround

tobias47n9e/pygobject-locale#1 (comment)

Change-Id: I7f381e4de0ad9796e27d4c8e1c2c9e2331f25e91

kiwi/ui/builderloader.py

@@ -22,6 +22,7 @@
 #
 
 import logging
+import platform
 
 from gi.repository import Gtk
 
@@ -90,6 +91,30 @@ def __init__(self, view, gladefile=None, domain=None, data=None):
         if domain is not None:
             self._builder.set_translation_domain(domain)
 
+        if platform.system() == 'Windows' and gladefile:
+            # Windows with python3 and Gtk3/pygi has this really nasty bug that
+            # translations are actually working, but somehow the enconding is
+            # messed up by Gtk. This might be fixed in newer versions of
+            # Gtk/pygi, but currently, we are stuck with 3.24 on Windows. Other
+            # References from a user with the same issue
+            # https://stackoverflow.com/questions/32037573/
+            # https://sourceforge.net/p/pygobjectwin32/tickets/22/
+            # https://bugzilla.gnome.org/show_bug.cgi?id=753991
+            # And the source of the workaround
+            # https://github.com/tobias47n9e/pygobject-locale/issues/1#issuecomment-222287650
+            import xml.etree.ElementTree as ET
+            from io import BytesIO
+            import gettext
+            tree = ET.parse(gladefile)
+            for node in tree.iter():
+                if 'translatable' in node.attrib:
+                    del node.attrib['translatable']
+                    node.text = gettext.dgettext(domain, node.text)
+            temp_file = BytesIO()
+            tree.write(temp_file, encoding='utf-8', xml_declaration=True)
+            data = temp_file.getvalue().decode()
+            gladefile = None
+
         if gladefile is not None:
             self._builder.add_from_file(gladefile)
         elif data is not None: