message: docs(Build): Provide helpful error message when docker is not available
  When running npm run commit.
diff: @@ -12,6 +12,21 @@ try {
  if (err.code != 'EEXIST') throw err
  }
  +dockerVersion = spawnSync('docker', ['--version'], {
  + env: process.env,
  + stdio: [ 'ignore', 'ignore', 'ignore' ]
  +})
  +if (dockerVersion.status != 0) {
  + console.error("Could not run the 'docker' command.")
  + console.error("This package requires Docker to build.")
  + console.error("")
  + console.error("Please find installation instructions at:")
  + console.error("")
  + console.error(" https://docs.docker.com/install/")
  + console.error("")
  + process.exit(dockerVersion.status)
  +}
  +
  // Ensure we have the 'dockcross' Docker build environment driver script
  const dockcross = path.join('build', 'dockcross')
  try {
  