When I was uploading 023-counter-cache-column, I ran into the following error
-----> Ruby app detected
-----> Compiling Ruby/Rails
-----> Using Ruby version: ruby-2.0.0
-----> Installing dependencies using 1.5.2
New app detected loading default bundler cache
Running: bundle install --without development:test --path vendor/bundle --binstubs vendor/bundle/bin -j4 --deployment
Fetching gem metadata from https://rubygems.org/..........
Fetching additional metadata from https://rubygems.org/..
Could not find sprockets-2.11.1 in any of the sources
Bundler Output: Fetching gem metadata from https://rubygems.org/..........
Fetching additional metadata from https://rubygems.org/..
Could not find sprockets-2.11.1 in any of the sources
!
! Failed to install gems via Bundler.
!
! Push rejected, failed to compile Ruby app
The issue was with my Gemfile.lock. I needed to run bundle update to make sure this file was updated. After I ran bundle update sprockets changed to version 2.11.0. This makes the error understandable because 2.11.1 would be unavailable through rubygems.org unless specified.
Referenced StackOverflow