When deploying heroku app I get push rejected error (Precompiling assets failed)
<p>This is app that I am trying to push on heroku: <a href="https://github.com/kunokdev/flightmap" rel="nofollow">https://github.com/kunokdev/flightmap</a> however I get <code>Precompiling assets failed</code> error and <code>Push rejected to ...</code> log. What might cause this?</p>

<pre><code>remote:        /tmp/build_b9c70fb95f66f6b57f7d5868507a42de/vendor/bundle/ruby/2.2.0/gems/sprockets-rails-3.0.4/lib/sprockets/rails/task.rb:67:in `block (2 levels) in define'
remote:        Tasks: TOP =&gt; assets:precompile
remote:        (See full trace by running task with --trace)
remote:  !
remote:  !     Precompiling assets failed.
remote:  !
remote: 
remote:  !     Push rejected, failed to compile Ruby app
remote: 
remote: Verifying deploy...
remote: 
remote: !   Push rejected to flightmap.
remote: 
To ssh://git@heroku.com/flightmap.git
 ! [remote rejected] master -&gt; master (pre-receive hook declined)
error: failed to push some refs to 'ssh://git@heroku.com/flightmap.git'
kunok@Kunok:~/dev/flightmap$ 
</code></pre>

<p>This is my gemfile:</p>

<pre><code>source 'https://rubygems.org'


gem 'rails', '4.2.2'
# Use SCSS for stylesheets
gem 'sass-rails', '~&gt; 5.0'
# Use Uglifier as compressor for JavaScript assets
gem 'uglifier', '&gt;= 1.3.0'
# Use jquery as the JavaScript library
gem 'jquery-rails'
# Turbolinks makes following links in your web application faster. Read more: https://github.com/rails/turbolinks
gem 'turbolinks'
# Build JSON APIs with ease. Read more: https://github.com/rails/jbuilder
gem 'jbuilder', '~&gt; 2.0'
# bundle exec rake doc:rails generates the API under doc/api.
gem 'sdoc', '~&gt; 0.4.0', group: :doc
# rake
gem 'rake', '11.1.2'
# csv reader
gem 'smarter_csv'
# bower rails
gem 'bower-rails'
# angular templates
gem 'angular-rails-templates'
# angular material
gem 'rails-angular-material'
# ionicons
gem 'ionicons-rails'
# Get user location info
gem 'geocoder'

group :development, :test do
  # Call 'byebug' anywhere in the code to stop execution and get a debugger console
  gem 'byebug'
  # Use sqlite3 as the database for Active Record
  gem 'sqlite3'
end

  # Spring speeds up development by keeping your application running in the background. Read more: https://github.com/rails/spring
  gem 'spring'

group :development do
  # Access an IRB console on exception pages or by using &lt;%= console %&gt; in views
  gem 'web-console', '~&gt; 2.0'
end

group :test do
  gem 'minitest-reporters', '1.0.5'
  gem 'mini_backtrace',     '0.1.3'
  gem 'guard-minitest',     '2.3.1'
end

group :production do
  gem 'pg'
  gem 'rails_12factor'
end

ruby "2.2.1"
</code></pre>