Timeout when fetching source data from NicoSeiga

[evazion]

• http://danbooru.donmai.us/uploads/new?url=http://seiga.nicovideo.jp/seiga/im7749621

• http://danbooru.donmai.us/artists?search[url_matches]=http://seiga.nicovideo.jp/user/illust/71171642

Currently anything that involves fetching source data from NicoSeiga is timing out. This includes uploading with the bookmarklet, fetching source data, and searching for artists.

The immediate cause is that after we login to NicoSeiga, we get redirected to www.nicovideo.jp, which is currently down. See here: http://blog.nicovideo.jp/en_info/2017/12/post-067621.html.

The broader issue is not handling network problems gracefully. We should:

• avoid the request to www.nicovideo.jp (it's unnecessary overhead even when it works)

• have timeouts on all outgoing HTTP requests.

• expect HTTP requests to fail and handle failures gracefully when they do occur.