use sha256 hashes from warehouse

[graingert]

Generating hashes is too slow, use the hashes from warehouse.

eg: click the SHA256 buttons: https://pypi.org/project/gitchart/#files

[vphilippon]

@graingert Is this still needed/relevent with #557 merged?

[graingert]

Yes. Means you don't have to download the package to get the hash

[Mogost]

That is really good idea to get hashes from warehouse.
It speeds up a lot
It would be nice to have as an option.

[graingert]

@atugushev does this still need the needs discussion Need some more discussion

[atugushev]

@graingert I think so. Is there an API where we could get hashes from warehouse?

[graingert]

@atugushev https://warehouse.readthedocs.io/api-reference/json/

[atugushev]

@graingert cool, thanks!

[graingert]

@atugushev it also includes package dependency information which would save downloading any packages at all

[atugushev]

I made a PR #1109, please test/review. Thanks!