How to handle rake errors during the build

Hi,

I'm trying to setup TeamCity to deploy my Ruby-on-Rails application to Heroku.
I use Rake script, that deploys the code to the remote Heroku repo and restarts servers and also performs database migrations.

Actually in case of normal flow, everything works well, but if Rake-task fails with some error, the whole build doesn't fail.
It even not always shows the errors in build log (for example, when migrations could not be done because of constraints violation)
Could you please advice what I'm doing wrong and how can I achieve the expected behavior?
I'm using script like this:

#Deploy and rollback on Heroku in staging and production
task :deploy_staging => ['deploy:set_staging_app', 'deploy:push', 'deploy:restart']
task :deploy_production => ['deploy:set_production_app', 'deploy:push', 'deploy:restart', 'deploy:tag']
task :migrate_staging => ['deploy:set_staging_app', 'deploy:migrate' ]
namespace :deploy do
  PRODUCTION_APP = 'my_app_name'
  STAGING_APP = 'my_app_name'
 
  task :staging_migrations => [:set_staging_app,:off, :migrate, :restart, :on]
  task :staging_rollback => [:set_staging_app, :off, :push_previous, :restart, :on]
 
  task :production_migrations => [:set_production_app, :push, :off, :migrate, :restart, :on, :tag]
  task :production_rollback => [:set_production_app, :off, :push_previous, :restart, :on]
 
  task :set_staging_app do
    APP = STAGING_APP
  end
 
  task :set_production_app do
       APP = PRODUCTION_APP
  end
 
  task :push do
    puts 'Deploying site to Heroku ...'
    puts `git push -f git@heroku.com:#{APP}.git`
  end
  
  task :restart do
    puts 'Restarting app servers ...'
    Bundler.with_clean_env { "heroku restart --app #{APP}"}
  end
  
  task :tag do
    release_name = "#{APP}_release-#{Time.now.utc.strftime("%%Y%%m%%d%%H%%M%%S")}"
    puts "Tagging release as '#{release_name}'"
    puts `git tag -a #{release_name} -m 'Tagged release'`
    puts `git push --tags git@heroku.com:#{APP}.git`
  end
  
  task :migrate do
    puts 'Running database migrations ...'
    Bundler.with_clean_env {"heroku run rake db:migrate --app #{APP}"}
  end
  
  task :off do
    puts 'Putting the app into maintenance mode ...'
    Bundler.with_clean_env {"heroku maintenance:on --app #{APP}"}
  end
  
  task :on do
    puts 'Taking the app out of maintenance mode ...'
    Bundler.with_clean_env {"heroku maintenance:off --app #{APP}"}
  end
 
  task :push_previous do
    prefix = "#{APP}_release-"
    releases = `git tag`.split("\n").select { |t| t[0..prefix.length-1] == prefix }.sort
    current_release = releases.last
    previous_release = releases[-2] if releases.length >= 2
    if previous_release
      puts "Rolling back to '#{previous_release}' ..."
      
      puts "Checking out '#{previous_release}' in a new branch on local git repo ..."
      puts `git checkout #{previous_release}`
      puts `git checkout -b #{previous_release}`
      
      puts "Removing tagged version '#{previous_release}' (now transformed in branch) ..."
      puts `git tag -d #{previous_release}`
      puts `git push git@heroku.com:#{APP}.git :refs/tags/#{previous_release}`
      
      puts "Pushing '#{previous_release}' to Heroku master ..."
      puts `git push git@heroku.com:#{APP}.git +#{previous_release}:master --force`
      
      puts "Deleting rollbacked release '#{current_release}' ..."
      puts `git tag -d #{current_release}`
      puts `git push git@heroku.com:#{APP}.git :refs/tags/#{current_release}`
      
      puts "Retagging release '#{previous_release}' in case to repeat this process (other rollbacks)..."
      puts `git tag -a #{previous_release} -m 'Tagged release'`
      puts `git push --tags git@heroku.com:#{APP}.git`
      
      puts "Turning local repo checked out on master ..."
      puts `git checkout master`
      puts 'All done!'
    else
      puts "No release tags found - can't roll back!"
      puts releases
    end
  end
end