Fix metamorphose#16 locales error with Python 2

Simply a workaround to ensure the call to locale.getlocale returns a valid locale.
Not sure if this the best solution (not a Python programmer -- yet!) but it works.
Have used this patch fine for 2 years now on my own Ubuntu 16.04 based system.

src/MainWindow/__init__.py

@@ -497,6 +497,9 @@ def set_language(self):
         app.language = language
         app.debug_print("Set language: " + app.language)
 
+        # hacked by Rob Savoury to fix #16 locales error with Python 2
+        locale.setlocale(locale.LC_ALL,'')
+
         self.encoding = unicode(locale.getlocale()[1])
         app.debug_print("Set encoding: " + self.encoding)