fail log

-----> Static Jekyll app detected
Successfully installed bundler-1.13.1
Parsing documentation for bundler-1.13.1
Installing ri documentation for bundler-1.13.1
Done installing documentation for bundler after 5 seconds
1 gem installed
Fetching gem metadata from https://rubygems.org/..........
Fetching version metadata from https://rubygems.org/..
Fetching dependency metadata from https://rubygems.org/.
Installing blankslate 2.1.2.4
Installing hitimes 1.2.2 with native extensions
Installing fast-stemmer 1.0.2 with native extensions
Installing coffee-script-source 1.9.1.1
Installing execjs 2.5.2
Installing colorator 0.1
Installing ffi 1.9.9 with native extensions
Installing jekyll-gist 1.2.1
Installing jekyll-paginate 1.1.0
Installing rb-fsevent 0.9.5
Installing kramdown 1.7.0
Installing sass 3.4.15
Installing liquid 2.6.2
Installing mercenary 0.3.5
Installing posix-spawn 0.3.11 with native extensions
Installing yajl-ruby 1.2.1 with native extensions
Installing redcarpet 3.3.2 with native extensions
Installing safe_yaml 1.0.4
Using bundler 1.13.1
Installing parslet 1.5.0
Installing ref 1.0.5
Installing libv8 3.16.14.8 with native extensions
Installing classifier-reborn 2.0.3
Installing timers 4.0.1
Installing coffee-script 2.4.1
Installing rb-inotify 0.9.5
Installing jekyll-sass-converter 1.3.0
Installing pygments.rb 0.6.3
Installing toml 0.1.2
Installing celluloid 0.16.0
Installing jekyll-coffeescript 1.0.1
Installing listen 2.10.1
Installing therubyracer 0.12.2 with native extensions
Installing jekyll-watch 1.2.1
Installing jekyll 2.5.3
Bundle complete! 2 Gemfile dependencies, 35 gems now installed.
Gems in the groups development and test were not installed.
Bundled gems are installed into /app/tmp/cache.
{"source"=>"/tmp/build_1f7588c4fbdc3b36e79d0c082122c0b8", "destination"=>"/tmp/build_1f7588c4fbdc3b36e79d0c082122c0b8/public_html/"}
Configuration file: /tmp/build_1f7588c4fbdc3b36e79d0c082122c0b8/_config.yml
-----> Failed to detect set buildpack https://codon-buildpacks.s3.amazonaws.com/buildpacks/heroku/ruby.tgz
More info: https://devcenter.heroku.com/articles/buildpacks#detection-failure
 !     Push failed