Heroku push rejected - heroku

Question

-----> Ruby/Rack app detected
-----> Using Ruby version: ruby-1.9.3
-----> Installing dependencies using Bundler version 1.3.0.pre.2
Running: bundle install --without development:test --path vendor/bundle --binstubs bin/
Fetching gem metadata from http://rubygems.org/.........
Fetching gem metadata from http://rubygems.org/..
^[[C^[[D^[[D/app/slug-compiler/lib/utils.rb:66:in `block (2 levels) in spawn': command='/app/slug-compiler/lib/../../tmp/buildpacks/ruby/bin/compile /tmp/build_22uiq5k0q45sp /app/tmp/repo.git/.cache' exit_status=0 out='' at=timeout elapsed=900.1076555252075 (Utils::TimeoutError)
from /app/slug-compiler/lib/utils.rb:52:in `loop'
from /app/slug-compiler/lib/utils.rb:52:in `block in spawn'
from /app/slug-compiler/lib/utils.rb:47:in `popen'
from /app/slug-compiler/lib/utils.rb:47:in `spawn'
from /app/slug-compiler/lib/buildpack.rb:37:in `block in compile'
from /app/slug-compiler/lib/buildpack.rb:35:in `fork'
from /app/slug-compiler/lib/buildpack.rb:35:in `compile'
from /app/slug-compiler/lib/slug.rb:497:in `block in run_buildpack'
from /app/slug-compiler/lib/utils.rb:121:in `log'
from /app/slug-compiler/lib/slug.rb:748:in `log'
from /app/slug-compiler/lib/slug.rb:496:in `run_buildpack'
from /app/slug-compiler/lib/slug.rb:125:in `block (2 levels) in compile'
from /app/slug-compiler/lib/utils.rb:102:in `block in timeout'
from /usr/local/lib/ruby/1.9.1/timeout.rb:58:in `timeout'
from /app/slug-compiler/lib/utils.rb:102:in `rescue in timeout'
from /app/slug-compiler/lib/utils.rb:97:in `timeout'
from /app/slug-compiler/lib/slug.rb:114:in `block in compile'
from /app/slug-compiler/lib/utils.rb:121:in `log'
from /app/slug-compiler/lib/slug.rb:748:in `log'
from /app/slug-compiler/lib/slug.rb:113:in `compile'
from /app/slug-compiler/bin/slugc:85:in `block in '
from /app/slug-compiler/lib/slug.rb:505:in `block in lock'
from /app/slug-compiler/lib/repo_lock.rb:44:in `call'
from /app/slug-compiler/lib/repo_lock.rb:44:in `run'
from /app/slug-compiler/lib/slug.rb:505:in `lock'
from /app/slug-compiler/bin/slugc:66:in `'
! Heroku push rejected, failed to compile Ruby/rack app
Here is my Gemfile:
source :rubygems
ruby '1.9.3'
gem 'sinatra', '1.3.3'
gem 'sinatra-contrib', '1.3.2'
gem 'thin', '1.5.0'
gem 'haml', '3.1.6'
gem 'bcrypt-ruby', '3.0.1'
gem 'mongo', '1.8.0'
gem 'bson_ext', '1.8.0'
gem 'mongoid', '3.0.16'
gem 'sinatra-flash', '0.3.0'
gem 'braintree', '2.22.0'
gem 'faye', '0.8.6'
#gem 'pony'
The error is gone when I change
gem 'braintree', '2.22.0'
to
gem 'braintree'

Answer 1

UPDATE: This answer doesn't work. The only option is to raise a support ticket.
There's a new feature that fixes this problem:
$ heroku config:set COMPILE_TIMEOUT=n
where n is a number in seconds. I used n=3000 (default is 900).
(note: you may need user-env-compile enabled to use this feature)
Update: Please read the comments on this answer for updated information!

Answer 2

For me the solution that I found was:
Push first half of my dependencies (half of the requirements.txt file)
Push all the requirements.txt file (including opencv dependency), this work because heroku keep in cached the first half, so then the second installation will go more fast