it('should resolve an absolute server url to a download url', (done) => {
   let contextPromise = context.getDownloadUrl('foo');
   let contentsPromise = manager.contents.getDownloadUrl('foo');
   Promise.all([contextPromise, contentsPromise])
   .then(values => {
     expect(values[0]).to.be(values[1]);
     done();
   }).catch(done);
 });
 it('should ignore urls that have a protocol', (done) => {
   context.getDownloadUrl('http://foo').then(path => {
     expect(path).to.be('http://foo');
     done();
   }).catch(done);
 });