mail: check files are PDF before importing them (#13509)

welco/sources/mail/management/commands/feed_mail.py

@@ -36,6 +36,8 @@ class Command(BaseCommand):
         for filepath in args:
             if not os.path.exists(filepath):
                 continue
+            if not open(filepath).read(5) == '%PDF-':
+                continue
             mail = Mail(content=File(open(filepath)))
             mail.scanner_category = kwargs.get('category')
             mail.save()