hydra-works update errors in sufia

Notes.md

When I update to rely on the latest hydra-works instead of relying on commit 4164209 (see Gemfile.extra), the tests for derivative creation break.

For example:

This line https://github.com/projecthydra/sufia/blob/pcdm/spec/services/create_derivatives_service_spec.rb#L27

       it 'lacks a thumbnail' do
        expect(@generic_file.thumbnail).not_to have_content
       end

Fails with

Failure/Error: expect(@generic_file.thumbnail).not_to have_content
       expected  to respond to `has_content?`

And this line https://github.com/projecthydra/sufia/blob/pcdm/spec/services/create_derivatives_service_spec.rb#L31

      it 'generates a thumbnail on job run' do
        subject.create_derivatives
        expect(@generic_file.thumbnail).to have_content
        expect(@generic_file.thumbnail.mime_type).to eq('image/jpeg')
      end

Fails with

Failure/Error: subject.create_derivatives
     NoMethodError:
       undefined method `has_content?' for nil:NilClass