Do not persist messages across generation sessions

scripts/compile_lang.py

@@ -10,4 +10,5 @@ for name in glob.iglob(locale_path + '/**'):
     if not os.path.isfile(name):
         path = os.path.join(locale_path, name, 'LC_MESSAGES', 'lang')
         sys.argv[1:] = [path + '.po']
+        msgfmt.reset()
         msgfmt.main()

scripts/msgfmt.py

@@ -92,6 +92,12 @@ def generate():
     return output
 
 
+def reset():
+    "Reset module state."
+    global MESSAGES
+    MESSAGES.clear()
+
+
 def make(filename, outfile):
     ID = 1
     STR = 2