Grunt Error

[gustavobuarque]

I have created a simple template and I'm trying to compile my LESS files. However, I'm getting the following error:

Verifying property exec.base exists in config...ERROR

Unable to process task.
Warning: Required config property "exec.base" missing. Use --force to continue.
Aborted due to warnings.

I started running the command bin/setup-grunt.

How can I fix this error?

grunt-config.json
{ "themes": "dev/tools/grunt/configs/themes" }
themes.js
... tema: { area: 'frontend', name: 'Engrama/tema', locale: 'pt_BR', files: [ 'css/styles-m', 'css/styles-l' ], dsl: 'less' } ...
Gruntfile.js

module.exports = function (grunt) {
'use strict';

var _ = require('underscore'),
    path = require('path'),
    filesRouter = require('./dev/tools/grunt/tools/files-router'),
    configDir = './dev/tools/grunt/configs',
    tasks = grunt.file.expand('./dev/tools/grunt/tasks/*'),
    themes;

filesRouter.set('themes', 'dev/tools/grunt/configs/themes.js');

...