Guard+Spork Issue (Guard::Spork failed to achieve its <start>,)

Question

I ran Guard with Spork following Rails Tutorial by Michael Hartl and I confronted this issue. Below is the error message:

20:45:58 - INFO - Starting Spork for RSpec, Test::Unit
20:45:58 - ERROR - Guard::Spork failed to achieve its <start>, exception was:
> [#B57790298EE3] ChildProcess::LaunchError: No such file or directory - bundle exec spork -p 8989
> [#B57790298EE3] /home/us/.rvm/gems/ruby-2.0.0-p0/gems/childprocess-0.3.9/lib/childprocess/unix/fork_exec_process.rb:54:in `l\aunch_process'
> [#B57790298EE3] /home/us/.rvm/gems/ruby-2.0.0-p0/gems/childprocess-0.3.9/lib/childprocess/abstract_process.rb:72:in `start'
> [#B57790298EE3] /home/us/.rvm/gems/ruby-2.0.0-p0/gems/guard-spork-1.2.0/lib/guard/spork/spork_instance.rb:38:in `start'

> [#B57790298EE3] /home/us/.rvm/gems/ruby-2.0.0-p0/gems/guard-spork-1.2.0/lib/guard/spork/runner.rb:33:in `each'
> [#B57790298EE3] /home/us/.rvm/gems/ruby-2.0.0-p0/gems/guard-spork-1.2.0/lib/guard/spork/runner.rb:33:in `launch_sporks'

> [#B57790298EE3] /home/us/.rvm/gems/ruby-2.0.0-p0/gems/guard-spork-1.2.0/lib/guard/spork.rb:21:in `start'
> [#B57790298EE3] /home/us/.rvm/gems/ruby-2.0.0-p0/gems/guard-1.7.0/lib/guard/runner.rb:99:in `block in run_supervised_task'
> [#B57790298EE3] /home/us/.rvm/gems/ruby-2.0.0-p0/gems/guard-1.7.0/lib/guard/runner.rb:97:in `catch'
> [#B57790298EE3] /home/us/.rvm/gems/ruby-2.0.0-p0/gems/guard-1.7.0/lib/guard/runner.rb:97:in `run_supervised_task'
> [#B57790298EE3] /home/us/.rvm/gems/ruby-2.0.0-p0/gems/guard-1.7.0/lib/guard/runner.rb:54:in `block (2 levels) in run'
> [#B57790298EE3] /home/us/.rvm/gems/ruby-2.0.0-p0/gems/guard-1.7.0/lib/guard/runner.rb:175:in `block (3 levels) in scoped_gua\rds'
> [#B57790298EE3] /home/us/.rvm/gems/ruby-2.0.0-p0/gems/guard-1.7.0/lib/guard/runner.rb:174:in `each'
> [#B57790298EE3] /home/us/.rvm/gems/ruby-2.0.0-p0/gems/guard-1.7.0/lib/guard/runner.rb:174:in `block (2 levels) in scoped_gua\rds'
> [#B57790298EE3] /home/us/.rvm/gems/ruby-2.0.0-p0/gems/guard-1.7.0/lib/guard/runner.rb:173:in `catch'
> [#B57790298EE3] /home/us/.rvm/gems/ruby-2.0.0-p0/gems/guard-1.7.0/lib/guard/runner.rb:173:in `block in scoped_guards'
> [#B57790298EE3] /home/us/.rvm/gems/ruby-2.0.0-p0/gems/guard-1.7.0/lib/guard/runner.rb:172:in `each'
> [#B57790298EE3] /home/us/.rvm/gems/ruby-2.0.0-p0/gems/guard-1.7.0/lib/guard/runner.rb:172:in `scoped_guards'
> [#B57790298EE3] /home/us/.rvm/gems/ruby-2.0.0-p0/gems/guard-1.7.0/lib/guard/runner.rb:53:in `block in run'
> [#B57790298EE3] /home/us/.rvm/gems/ruby-2.0.0-p0/gems/lumberjack-1.0.3/lib/lumberjack.rb:27:in `unit_of_work'
> [#B57790298EE3] /home/us/.rvm/gems/ruby-2.0.0-p0/gems/guard-1.7.0/lib/guard/runner.rb:52:in `run'
> [#B57790298EE3] /home/us/.rvm/gems/ruby-2.0.0-p0/gems/guard-1.7.0/lib/guard.rb:189:in `block in start'
> [#B57790298EE3] /home/us/.rvm/gems/ruby-2.0.0-p0/gems/guard-1.7.0/lib/guard.rb:365:in `block in within_preserved_state'

> [#B57790298EE3] /home/us/.rvm/gems/ruby-2.0.0-p0/gems/guard-1.7.0/lib/guard.rb:362:in `synchronize'
> [#B57790298EE3] /home/us/.rvm/gems/ruby-2.0.0-p0/gems/guard-1.7.0/lib/guard.rb:362:in `within_preserved_state'
> [#B57790298EE3] /home/us/.rvm/gems/ruby-2.0.0-p0/gems/guard-1.7.0/lib/guard.rb:187:in `start'
> [#B57790298EE3] /home/us/.rvm/gems/ruby-2.0.0-p0/gems/guard-1.7.0/lib/guard/cli.rb:110:in `start'
> [#B57790298EE3] /home/us/.rvm/gems/ruby-2.0.0-p0/gems/thor-0.18.1/lib/thor/command.rb:27:in `run'
> [#B57790298EE3] /home/us/.rvm/gems/ruby-2.0.0-p0/gems/thor-0.18.1/lib/thor/invocation.rb:120:in `invoke_command'
> [#B57790298EE3] /home/us/.rvm/gems/ruby-2.0.0-p0/gems/thor-0.18.1/lib/thor.rb:363:in `dispatch'
> [#B57790298EE3] /home/us/.rvm/gems/ruby-2.0.0-p0/gems/thor-0.18.1/lib/thor/base.rb:439:in `start'
> [#B57790298EE3] /home/us/.rvm/gems/ruby-2.0.0-p0/gems/guard-1.7.0/bin/guard:6:in `<top (required)>'
> [#B57790298EE3] ./bundler_stubs/guard:16:in `load'
> [#B57790298EE3] ./bundler_stubs/guard:16:in `<main>'
20:45:58 - INFO - Guard::Spork has just been fired

Spork can execute with no problem:

Using RSpec
Preloading Rails environment
Loading Spork.prefork block...
Spork is ready and listening on 8989!

What seemed to be the problem? Is there a bug in childprocess-0.3.9? Or My Guardfile? Below is the my Guardfile:

# A sample Guardfile
# More info at https://github.com/guard/guard#readme

guard 'rspec', :version => 2, :all_after_pass => false, :cli => '--drb' do
  watch(%r{^spec/.+_spec\.rb$})
  watch(%r{^lib/(.+)\.rb$})     { |m| "spec/lib/#{m[1]}_spec.rb" }
  watch('spec/spec_helper.rb')  { "spec" }

  # Rails example
  watch(%r{^app/(.+)\.rb$})                           { |m| "spec/#{m[1]}_spec.rb" }
  watch(%r{^app/(.*)(\.erb|\.haml)$})                 { |m| "spec/#{m[1]}#{m[2]}_spec.rb" }
  watch(%r{^app/controllers/(.+)_(controller)\.rb$})  { |m| ["spec/routing/#{m[1]}_routing_spec.rb", "spec/#{m[2]}s/#{m[1]}_#{\m[2]}_spec.rb", "spec/acceptance/#{m[1]}_spec.rb", (m[1][/_pages/] ? "spec/requests/#{m[1]}_spec.rb" : "spec/requests/#{m[1].s\ingularize}_pages_spec.rb")] }
  watch(%r{^spec/support/(.+)\.rb$})                  { "spec" }
  watch('config/routes.rb')                           { "spec/routing" }
  watch('app/controllers/application_controller.rb')  { "spec/controllers" }

  # Capybara request specs
  watch(%r{^app/views/(.+)/}) do |m|
    (m[1][/_pages/] ? "spec/requests/#{m[1]}_spec.rb" :
     "spec/requests/#{m[1].singularize}_pages_spec.rb")
  end

  # Turnip features and steps
  watch(%r{^spec/acceptance/(.+)\.feature$})
  watch(%r{^spec/acceptance/steps/(.+)_steps\.rb$})   { |m| Dir[File.join("**/#{m[1]}.feature")][0] || 'spec/acceptance' }

end

guard 'spork', :rspec_env => { 'RAILS_ENV' => 'test' } do
  watch('config/application.rb')
  watch('config/environment.rb')
  watch('config/environments/test.rb')
  watch(%r{^config/environments/.+\.rb$})
  watch(%r{^config/initializers/.+\.rb$})
  watch('Gemfile')
  watch('Gemfile.lock')
  watch('spec/spec_helper.rb')
  watch('test/test_helper.rb')
  watch('spec/support/')
end

Answer 1

quoting from Error on start when using Spork and Guard

"That's a known issue in guard-spork and you can either use the previous 
version of ChildProcess by adding

gem 'childprocess', '0.3.6'

to your Gemfile or try the guard-spork master branch, which has fixed 
the issue by adding

gem 'guard-spork', :github => 'guard/guard-spork'

to your Gemfile."

I went with the :github => 'guard/guard-spork' approach and everything works now