old_contents: /*!
   * Project: mp3web
   * File:    ./gulp-tasks/env/replvars.js
   * Author:  Baltrushaitis Tomas <tbaltrushaitis@gmail.com>
   * Created: 2017-12-19T13:28:00
   * Updated: 2017-12-19T13:28:00
   */
  
  'use strict';
  
  /**
   * DEPENDENCIES
   * @private
   */
  
  const path = require('path');
  const util = require('util');
  const _ = require('lodash');
  
  const buffer = require('vinyl-buffer');
  const replace = require('gulp-replace');
  const rename = require('gulp-rename');
  const concat = require('gulp-concat');
  
  const modName = path.basename(module.filename, '.js');
  const modPath = path.relative(global.ME.WD, path.dirname(module.filename));
  
  const modConfigFile = `config/${path.join(modPath, modName)}.json`;
  const modConfig = require('read-config')(modConfigFile);
  
  const utin = util.inspect;
  
  //  ------------------------------------------------------------------------  //
  //  -------------------------------  EXPOSES  ------------------------------  //
  //  ------------------------------------------------------------------------  //
  
  module.exports = function (gulp) {
    console.log(`[${new Date().toISOString()}][${modPath}/${modName}] INSTANCE ACTIVATED with modConfig = [${utin(modConfig)}]`);
  
    function replaceEnvironmentVariables (stream) {
      for (let cgv in modConfig) {
        let key = cgv.toUpperCase(),
            v = modConfig[cgv];
        v = _.isObject(v)
              ? JSON.stringify(v)
              : v;
  
        stream = stream.pipe(replace('{{' + key + '}}', v));
        console.log(`[${new Date().toISOString()}][${modPath}/${modName}] Replace ${key}:\t ${v}`);
      }
      stream = stream.pipe(replace('{{APP_VERSION}}', global.ME.pkg.version));
      return stream;
    };
  
    var process = gulp.src([
        path.join(global.ME.SRC, `.env.rc.test`)
      ])
      .pipe(buffer());
  
    process = replaceEnvironmentVariables(process);
    return process.pipe(concat('.env.rc.test.concat'))
            .pipe(gulp.dest(global.ME.BUILD));
  
  };
  
new_contents: /*!
   * Project: mp3web
   * File:    ./gulp-tasks/env/replvars.js
   * Author:  Baltrushaitis Tomas <tbaltrushaitis@gmail.com>
   * Created: 2017-12-19T13:28:00
   * Updated: 2017-12-19T13:28:00
   */
  
  'use strict';
  
  /**
   * DEPENDENCIES
   * @private
   */
  
  const path = require('path');
  const util = require('util');
  const _ = require('lodash');
  
  const buffer = require('vinyl-buffer');
  const replace = require('gulp-replace');
  const rename = require('gulp-rename');
  const concat = require('gulp-concat');
  
  const modName = path.basename(module.filename, '.js');
  const modPath = path.relative(global.ME.WD, path.dirname(module.filename));
  
  const modConfigFile = `config/${path.join(modPath, modName)}.json`;
  const modConfig = require('read-config')(modConfigFile);
  
  const utin = util.inspect;
  
  //  ------------------------------------------------------------------------  //
  //  -------------------------------  EXPOSES  ------------------------------  //
  //  ------------------------------------------------------------------------  //
  
  module.exports = function (gulp) {
    console.log(`[${new Date().toISOString()}][${modPath}/${modName}] INSTANCE ACTIVATED with modConfig = [${utin(modConfig)}]`);
  
    function replaceEnvironmentVariables (stream) {
      for (let cgv in modConfig) {
        let key = cgv.toUpperCase()
          , v   = modConfig[cgv]
        ;
        // v = _.isObject(v) ? v = JSON.stringify(v) : true;
        _.isObject(v) ? v = JSON.stringify(v) : true;
  
        stream = stream.pipe(replace('{{' + key + '}}', v));
        console.log(`[${new Date().toISOString()}][${modPath}/${modName}] Replace ${key}:\t ${v}`);
      }
      stream = stream.pipe(replace('{{APP_VERSION}}', global.ME.pkg.version));
      return stream;
    };
  
    let process = gulp.src([
        path.join(global.ME.SRC, `.env.rc.test`)
      ])
      .pipe(buffer());
  
    process = replaceEnvironmentVariables(process);
    return process.pipe(concat('.env.rc.test.concat'))
            .pipe(gulp.dest(global.ME.BUILD));
  
  };
  
subject: Replace 'var' to 'let'