code: function onExec( error ) {
  		if ( error ) {
  			debug( 'Error encountered while attempting to convert %s: %s', inFile, error.message );
  			return done( error );
  		}
  		debug( 'Successfully converted input file: %s', inFile );
  		unlink( inFile, onRemove );
  	}
docs: end FUNCTION onWrite() 
  FUNCTION: onExec( error, stdout, stderr )
  Callback invoked when the child process performing conversion terminates.
  
  @private
  @param {Error|Null} error - error object
  @param {Buffer} stdout - standard output
  @param {Buffer} stderr - standard error
  @returns {Void}