Update request.py

Change error string for ftp error to be consistent with other errors reported for ftp

Author: jeremyhylton

Lib/urllib/request.py

@@ -1555,7 +1555,7 @@ def ftp_open(self, req):
             headers = email.message_from_string(headers)
             return addinfourl(fp, headers, req.full_url)
         except ftplib.all_errors as exp:
-            raise URLError(exp.args[0]) from exp
+            raise URLError(f"ftp error: {exp}") from exp
 
     def connect_ftp(self, user, passwd, host, port, dirs, timeout):
         return ftpwrapper(user, passwd, host, port, dirs, timeout,