Heroku hangs on 'Cleaning up the bundler cache.' with oauth2 in gemfile - ruby

Question

I'm trying to push heroku master, and I can't get past 'Cleaning up the bundler cache.'
I've tracked down the issue to the oauth2 gem. If I remove that from the Gemfile, bundle install, and push the repo up to Heroku, it deploys just fine. However, my app can't run without it.
Locally, I'm able to run everything.
Logs:
> Initializing repository, done. Counting objects: 90, done. Delta
> compression using up to 4 threads. Compressing objects: 100% (82/82),
> done. Writing objects: 100% (90/90), 27.55 KiB | 0 bytes/s, done.
> Total 90 (delta 38), reused 0 (delta 0)
>
> -----> Ruby app detected
> -----> Compiling Ruby/Rack
> -----> Using Ruby version: ruby-1.9.3
> -----> Installing dependencies using 1.6.3
> Running: bundle install --without development:test --path vendor/bundle --binstubs vendor/bundle/bin -j4 --deployment
> Fetching gem metadata from http://rubygems.org/.........
> Fetching additional metadata from http://rubygems.org/..
> Installing minitest 5.4.2
> Installing i18n 0.6.11
> Installing thread_safe 0.3.4
> Installing builder 3.2.2
> Installing arel 5.0.1.20140414130214
> Installing mini_portile 0.6.0
> Installing multipart-post 2.0.0
> Installing jwt 1.0.0
> Installing rack 1.5.2
> Installing logger 1.2.8
> Installing systemu 2.6.4
> Installing multi_json 1.10.1
> Installing mime-types 2.4.1
> Installing multi_xml 0.5.5
> Installing netrc 0.7.7
> Installing nori 2.4.0
> Installing tilt 1.4.1
> Using bundler 1.6.3
> Installing tzinfo 1.2.2
> Installing gyoku 1.1.1
> Installing json 1.8.1
> Installing faraday 0.9.0
> Installing httpi 2.2.7
> Installing rack-protection 1.5.3
> Installing macaddr 1.7.1
> Installing rest-client 1.7.2
> Installing activesupport 4.1.6
> Installing oauth2 1.0.0
> Installing sinatra 1.4.5
> Installing uuid 2.3.7
> Installing stripe 1.16.0
> Installing activemodel 4.1.6
> Installing activerecord 4.1.6
> Installing sinatra-activerecord 2.0.2
> Installing pg 0.17.1
> Installing nokogiri 1.6.3.1
> Installing akami 1.2.2
> Installing wasabi 3.3.1
> Installing savon 2.7.2
> Installing tax_cloud 0.3.0
> Your bundle is complete!
> Gems in the groups development and test were not installed.
> It was installed into ./vendor/bundle
> Bundle completed (47.32s)
> Cleaning up the bundler cache.