Issue 16646 (ftplib): deliberately use intermediate variable after catching exception

Lib/ftplib.py

@@ -291,7 +291,8 @@ class FTP:
             try:
                 sock = socket.socket(af, socktype, proto)
                 sock.bind(sa)
-            except socket.error as err:
+            except socket.error as _:
+                err = _
                 if sock:
                     sock.close()
                 sock = None