jupyter-tramp-server-from-file-name: Fix password authenticator

fixes #480

Author: nnicandro

jupyter-rest-api.el

@@ -532,8 +532,9 @@ slot of CLIENT and restore the AUTH slot on failure."
                                         &optional passwd)
   "Authenticate CLIENT by asking for a password.
 If PASSWD is provided it must be a function that takes zero
-arguments.  It will be called before each authentication attempt.
-If CLIENT could not be authenticated raise an error."
+arguments and returns a password, it defaults to a call to
+`read-passwd'.  It will be called before each authentication
+attempt.  If CLIENT could not be authenticated raise an error."
   (or (functionp passwd)
       (setq passwd (lambda () (read-passwd (format "Password [%s]: "
                                               (oref client url))))))

jupyter-tramp.el

@@ -312,10 +312,9 @@ fails."
               (jupyter-api-authenticate client
                 'password
                 (let ((remote (file-remote-p filename)))
-                  (lambda (try)
+                  (lambda ()
                     (jupyter-tramp-read-passwd
-                     filename (unless (zerop try)
-                                (format "Password for %s " remote))))))))))))))
+                     filename (format "Password [%s]: " remote)))))))))))))
 
 ;;; Getting information about file models