code: function runSpac(schemaFilePath, namespace, outputDir) {
    var spacPath = pathMod.resolve(pathMod.join(__dirname, '../spac/spac.js'));
    var spac = childProcess.fork(
        spacPath,
        [
          '--schema=' + schemaFilePath,
          '--namespace=' + namespace,
          '--outputdir=' + outputDir,
          '--nocombine=true'
        ]);
  
    return new Promise(function(resolve, reject) {
      spac.on('close', function(code) {
        if (code == 0) {
          resolve();
        } else {
          var error = new Error(
              'ERROR: unable to generate code from ' + schemaFilePath + '\r\n');
          log(error);
          reject(error);
        }
      });
    });
  }
docs: Runs SPAC to generate code.
  @param {string} schemaFilePath
  @param {string} namespace
  @param {string} outputDir
  @return {!IThenable}