Add a backup of po files

lang/update-po.py

@@ -6,6 +6,7 @@ Portable script to update po files on most platforms
 
 import argparse
 from sys import stderr, exit
+import shutil
 from pathlib import Path
 import polib
 from polib import POFile
@@ -34,6 +35,9 @@ def main():
             return 1
 
     for po_file in PO_FILE_LIST:
+        # Start by creating a back-up of the .po file
+        po_file_bak = po_file.with_suffix(".bak")
+        shutil.copy(PO_DIR / po_file, PO_DIR / po_file_bak)
         po = polib.pofile(po_file)
         po.merge(POT_REFERENCE)
         po.save(po_file)