=== modified file 'Mailman/Cgi/options.py'
--- Mailman/Cgi/options.py	2019-03-06 17:48:32 +0000
+++ Mailman/Cgi/options.py	2020-04-20 03:10:16 +0000
@@ -173,7 +173,7 @@
     try:
         Utils.ValidateEmail(user)
     except Errors.EmailAddressError:
-        doc.addError(_('Illegal Email Address: %(safeuser)s'))
+        doc.addError(_('Illegal Email Address'))
         loginpage(mlist, doc, None, language)
         print doc.Format()
         return