anchor.diff:        }
         _logger.stderr('');
         _logger.stderr('It is highly recommended to upgrade all dependencies to '
  -          'versions which have migrated. Use `$_pubName outdated '
  +          'versions which have migrated. Use `dart pub outdated '
             '--mode=null-safety` to check the status of dependencies.');
         _logger.stderr('');
         _logger.stderr('Visit https://dart.dev/tools/pub/cmd/pub-outdated for '
  
positive.code: 
  @visibleForTesting
  class DependencyChecker {
    static final _pubName = Platform.isWindows ? 'pub.bat' : 'pub';
  
    /// The directory which contains the package being migrated.
    final String _directory;
    final Context _pathContext;
  
negative.code:       this._directory, this._pathContext, this._logger, this._processManager);
  
    bool check() {
      var pubPath = _pathContext.join(getSdkPath(), 'bin', 'dart');
      var pubArguments = ['pub', 'outdated', '--mode=null-safety', '--json'];
      var preNullSafetyPackages = <String, String>{};
      try {
        var result = _processManager.runSync(pubPath, pubArguments,
            workingDirectory: _directory);
        if ((result.stderr as String).isNotEmpty) {
          throw FormatException(
              '`dart pub outdated --mode=null-safety` exited with exit code '
              '${result.exitCode} and stderr:\n\n${result.stderr}');
        }
        var outdatedOutput = jsonDecode(result.stdout as String);
  