我运行以下命令（Mx）：
Install package: haskell-mode
然后我得到错误：
[No match]
我.emacs的是：
(require 'package)
(custom-set-variables
;; custom-set-variables was added by Custom.
;; If you edit it by hand, you could mess it up, so be careful.
;; Your init file should contain only one such instance.
;; If there is more than one, they won't work right.
'(package-archives
(quote
(("gnu" . "http://elpa.gnu.org/packages/")
("melpa-stable" . "http://stable.melpa.org/packages/")))))
(package-initialize)
我也跑了M-x package-refresh-contents。
如何调试此错误？