Cache mechanism for requests-ftp

[femtotrader]

Hello,

I wonder if requests-ftp could support cache. It will be great for https://github.com/pydata/pandas-datareader/pull/145 see https://github.com/pydata/pandas-datareader/issues/143

See also https://github.com/reclosedev/requests-cache/issues/57

Kind regards

[Lukasa]

I'm open to adding support for caching, but I don't think I'll add it myself: this project is basically in maintenance mode at this point.

[femtotrader]

It will be great if @reclosedev could tell us his opinion.

[graingert]

@femtotrader not sure how you're supposed to know if the file has changed or not, because there's no caching headers

There's a draft here https://tools.ietf.org/html/draft-bryan-ftpext-hash-02 which could be implemented