anchor.diff:  
   final _versionDownloadRexexp =
       new RegExp(r"^MSG : (?:Downloading |Already cached )([\w-]+) (.+)$");
  +
  +const _pubEnv = const <String, String>{
  +  'PUB_ENVIRONMENT': 'kevmoo.pkg_clean'
  +};
  
positive.code: 
    args.add(pkgName);
  
    Map<String, String> pubEnv;
    if (pubCachePath != null) {
      pubEnv = {'PUB_CACHE': pubCachePath};
    }
  
    var result = await Process.run('pub', args, environment: pubEnv);
  
negative.code: }
  
  Future<PubSummary> pkgSummary(String pkgPath, {String pubCachePath}) async {
    var pubEnv = new Map<String, String>.from(_pubEnv);
    if (pubCachePath != null) {
      pubEnv['PUB_CACHE'] = pubCachePath;
    }
  
    log.info('Running `pub upgrade`...');
  