anchor.diff:          var version = json.expectType<String>(current['version'], 'version');
           preNullSafetyPackages[name] = version;
         }
  +    } on ProcessException catch (e) {
  +      _logger.stderr(
  +          'Warning: Could not execute `$pubPath ${pubArguments.join(' ')}`: '
  +          '"${e.message}"');
  +      // Allow the program to continue; users should be allowed to attempt to
  +      // migrate when `pub outdated` is misbehaving, or if there is a bug above.
       } on FormatException catch (e) {
         _logger.stderr('Warning: ${e.message}');
         // Allow the program to continue; users should be allowed to attempt to
  
positive.code:       this._directory, this._pathContext, this._logger, this._processManager);
  
    bool check() {
      var pubPath = _pathContext.join(getSdkPath(), 'bin', _pubName);
      var result = _processManager.runSync(
          pubPath, ['outdated', '--mode=null-safety', '--json'],
          workingDirectory: _directory);
  
      var preNullSafetyPackages = <String, String>{};
      try {
        if ((result.stderr as String).isNotEmpty) {
          throw FormatException(
              '`pub outdated --mode=null-safety` exited with exit code '
              '${result.exitCode} and stderr:\n\n${result.stderr}');
        }
        var outdatedOutput = jsonDecode(result.stdout as String);
  
negative.code: 
  @visibleForTesting
  class DependencyChecker {
    /// The directory which contains the package being migrated.
    final String _directory;
    final Context _pathContext;
  