lib/classes/Variables.js/Variables/getValueFromEnv
class Variables:  getValueFromEnv(variableString) {
    // eslint-disable-line class-methods-use-this
    const requestedEnvVar = variableString.split(':')[1];
    let valueToPopulate;
    if (requestedEnvVar !== '' || '' in process.env) {
      valueToPopulate = process.env[requestedEnvVar];
    } else {
      valueToPopulate = process.env;
    }
    return BbPromise.resolve(valueToPopulate);
  }