Fixes #272. Turns out we were already passing through npm:XXX specifiers in
the Deno provider, so I've just improved the error message. I think I was
stupidly testing it with jspm install -p deno fresh, which uses the npm
registry by default, whereas I should have done jspm install -p deno denoland:fresh.
Fixes #272. Turns out we were already passing through
npm:XXXspecifiers in the Deno provider, so I've just improved the error message. I think I was stupidly testing it withjspm install -p deno fresh, which uses thenpmregistry by default, whereas I should have donejspm install -p deno denoland:fresh.