bug#20838: 25.0.50; Lisp error: (wrong-type-argument listp :error) when refreshing the package list

[Glenn Morris]

Tassilo Horn wrote:

> Since recently, I get the following error when refreshing the package
> list (M-x list-packages RET).
>
> --8<---------------cut here---------------start------------->8---
> Debugger entered--Lisp error: (wrong-type-argument listp :error)
>   #[257 "\211@\304=\203..\305\303!\203..\303 
> \210\306.@A.AA\"\210\202?.eb\210\307\310\311\312#\204,.\313\314p\"\210e`|\210\315\316
>  \302\301#\300\203>.\300.!\210\210\317p!\207" [#[256 
> "\211\204..\f\305=\204..\306\300!\210\307\310\301\"\210\311\302\312\303\312\313%\210\211\203-.\311\314\315.\316#\312\303\317P\312\313%\210\306\300!\207"
>  [("melpa" . "http://melpa.org/packages/";) "melpa" "\n(1 (zygospore . 
> [(20140703 152) nil \"reversible C-x 1 (delete-other-windows)\" single ((:url 
> . \"https://github.com/louiskottmann/zygospore.el\";))]) (ztree . [(20150613 
> 1328) nil \"Text mode directory tree\" tar ((:keywords \"files\" \"
tools\") (:url . \"https://github.com/fourier/ztree\";))]) (zotxt .
[(20150603 2017) ((request-deferred (0 2 0))) \"Tools to integrate emacs
with Zotero via the zotxt plugin.\" tar nil]) (zotelo . [(20150531 1225)
nil \"Manage Zotero coll


Snip truly enormous backtrace which was far too large to send out to
bug-gnu-emacs. Interested parties can see the full report at
http://debbugs.gnu.org/20838