Ran into this issue when running under ruby 2.3.x:
Injecting configuration and compiling…
e[1G-----> Ruby app detected
e[1G-----> Compiling Ruby
e[1G-----> Using Ruby version: ruby-2.3.1
…
e[1G NoMethodError: undefined method `spec’ for nil:NilClass
e[1G Installing unf_ext 0.0.7.1
e[1G Installing nokogiri 1.6.6.2
e[1G An error occurred while installing scraperwiki (3.0.1), and Bundler cannot
e[1G continue.
e[1G Make sure that `gem install scraperwiki -v ‘3.0.1’` succeeds before bundling.
e[1G !
e[1G ! Failed to install gems via Bundler.
e[1G !
The scraperwiki gem installs fine under the default ruby 2.0.0.
Bundler runs fine for ruby 2.3.x on my local environment.