getRequired(name) {
    var value = this.get(name);
    if (!value) {
      throw new Error('Configuration ' + name + ' is required.');
    }
    return value;
  }
Gets the configuration value for the given name. If an unrecognized name is
specified or the value is not provided, an `Error` is thrown.

@param {string} name The name of the configuration.
@return {*} The configuration value.