code: function registerPartials(src, options, prefix = '') {
    return readFiles(src.glob, options).then(partialFiles => {
      partialFiles.forEach(partialFile => {
        const partialKey = resourceId(partialFile, src.basedir, prefix);
        if (options.handlebars.partials.hasOwnProperty(partialKey)) {
          DrizzleError.error(
            new DrizzleError(
              `Partial key '${partialKey}' already
  registered on Handlebars instance: is this intentional?`,
              DrizzleError.LEVELS.WARN
            ),
            options
          );
        }
        options.handlebars.registerPartial(partialKey, partialFile.contents);
      });
    });
  }
docs: Register the files matching `src.glob` as partials. Keys are generated by
  using path relative to `src.basedir` separated by `.`
  @param {Object} src    Object with `path` and `basedir` props
  @see defaults
  @param {Object} options
  @param {String} prefix Gets passed to `resourceId` as the
  `resourceCollection` argument. @see utils/object
  @return {Promise}