After updated my DokuWiki to "Ponder Stibbons" release,
the extension manager shows a red error bar with "[Retry]" message.
The $lang['repo_error'] does not defined in the language file, but that is another issue.
The error indicates that access to the EXTENSION_REPOSITORY_API -
http://www.dokuwiki.org/lib/plugins/pluginrepo/api.php - failed from my host server. I have tried accessing to the API from server console using wget, and found that the API dose not respond through IPv6 to my server located in somewhere in Japan. Even access through IPv4 is available. I think this may be conserned with www.dokuwiki.org host issue rather than the extension plugin issue. I do not want to disabe IPv6 in my host.
$ wget "http://www.dokuwiki.org/lib/plugins/pluginrepo/api.php?cmd=ping"
--2014-05-10 16:25:17-- http://www.dokuwiki.org/lib/plugins/pluginrepo/api.php?cmd=ping
Resolving www.dokuwiki.org... 2a01:4f8:140:13e4::b00b, 46.4.55.201
Connecting to www.dokuwiki.org|2a01:4f8:140:13e4::b00b|:80... failed: Connection timed out.
Connecting to www.dokuwiki.org|46.4.55.201|:80... connected.
HTTP request sent, awaiting response... 200 OK
Length: unspecified [text/plain]
Saving to: `api.php?cmd=ping.1'
[ <=> ] 1 --.-K/s in 0s
2014-05-10 16:26:25 (86.0 KB/s) - `api.php?cmd=ping' saved [1]
I appreciate any suggestion on this issue.