Update util.js (#172)

Wrong variable name used

Author: ripkens

lib/util.js

@@ -135,7 +135,7 @@ function runExecIntoFile( label, filePath, options, execOptions, genCommand, cb
                 if ( error3 ) {
                   error3 = new Error( 'Error, ' + label +
                     ' , cleaning up temp file [[ ' + fileTempOutPath +
-                    ' ]], error: ' + error.message );
+                    ' ]], error: ' + error3.message );
                   cb( error3, null );
                 } else {
                   cb( null, text.toString() );