code: function onexit( code ) {
  		let changedFiles;
  
  		cssMake.stderr.removeListener( 'data', onstderr );
  		cssMake.stdout.removeListener( 'data', onstdout );
  		cssMake = null;
  
  		if ( scheduleBuild ) {
  			// Handle new css build request
  			scheduleBuild = false;
  			spawnMake();
  		} else if ( 0 === code ) {
  			// 'make build-css' success
  			changedFiles = updateChangedCssFiles();
  			if ( 0 !== changedFiles.length ) {
  				debug( chalk.green( 'css reload' ) );
  				io.of( '/css-hot-reload' ).emit( 'css-hot-reload', {
  					status: 'reload',
  					changedFiles: changedFiles,
  				} );
  			} else {
  				debug( chalk.green( 'css up to date' ) );
  				io.of( '/css-hot-reload' ).emit( 'css-hot-reload', { status: 'up-to-date' } );
  			}
  		} else {
  			// 'make build-css' failed
  			debug( chalk.red( 'css build failed' ) );
  			io.of( '/css-hot-reload' ).emit( 'css-hot-reload', {
  				status: 'build-failed',
  				error: errors,
  			} );
  		}
  	}
docs: Handle 'make build-css' success or failure
  @param {Number} code The exit code