Using a download cache for npm/python deps

With big npm.js issues today and no automated way of running new deps like tornado, a download cache of the packages needed with a make step that updates it would be a lot nicer these days.

We use a download-cache in Charmworld for all python and npm packages. They’re version frozen and installed only from the LP branch.

gary: benji has something that might help, based on charm work he did to build a branch in the charm quickly. [ACTION] Benji will propose something.

benji points out that this is fragile. jon points out that we change dependencies infrequently and so then we’ll fix it.

Ben and gary don’t encounter this much because they share dependencies across branches. Nicola copies directories ’cause it’s fun.