conflict gem versions

結論

$ bundle update

で解決しました。

原因

faraday という依存 gem のバージョンのコンフリクトです。
fog の方が古いようでしたので bundle update fog で解決しました

Bundler could not find compatible versions for gem "faraday":
  In snapshot (Gemfile.lock):
    faraday (= 0.17.0)

  In Gemfile:
    fog was resolved to 2.2.0, which depends on
      fog-google (~> 1.0) was resolved to 1.9.1, which depends on
        google-api-client (~> 0.23.0) was resolved to 0.23.9, which depends on
          googleauth (< 0.7.0, >= 0.5) was resolved to 0.6.7, which depends on
            faraday (~> 0.12)

    sentry-ruby was resolved to 4.2.2, which depends on
      faraday (>= 1.0)

Running `bundle update` will rebuild your snapshot from scratch, using only
the gems in your Gemfile, which may resolve the conflict.