old_contents: import subprocess
  
  def execute():
      subprocess.call([
          'npm', 'install',
          'babel-core',
          'chokidar',
          'babel-preset-es2015',
          'babel-preset-es2016',
          'babel-preset-es2017',
          'babel-preset-babili'
      ])
new_contents: from subprocess import Popen, call, PIPE
  
  def execute():
      # update nodejs version if brew exists
      p = Popen(['which', 'brew'], stdout=PIPE, stderr=PIPE)
      output, err = p.communicate()
      if output:
          subprocess.call(['brew', 'upgrade', 'node'])
      else:
          print 'Please update your NodeJS version'
  
      subprocess.call([
          'npm', 'install',
          'babel-core',
          'less',
          'chokidar',
          'babel-preset-es2015',
          'babel-preset-es2016',
          'babel-preset-es2017',
          'babel-preset-babili'
      ])
subject: Update build system requirements patch