Polyfill fetch() for tests

Summary: Per title. Required as Scribe is now being used for device tests.

Reviewed By: jknoxville, danielbuechele

Differential Revision: D13971892

fbshipit-source-id: 2df36d44d4e45a579cc9cca0d4cad9105ba8a383

static/globalTestSetup.js

@@ -12,3 +12,5 @@ console.error = function(message) {
   );
   defaultConsoleError.apply(console, arguments);
 };
+
+global.fetch = require('jest-fetch-mock');