anchor.diff:    final _packagesWithVersion = <String>{};
     final _publishers = <String>{};
     final _publishersAbandoned = <String>{};
  +  // package name -> versions
  +  final _badVersionInPubspec = <String, Set<String>>{};
     int _packageChecked = 0;
     int _versionChecked = 0;
     late http.Client _httpClient;
  
positive.code:       yield 'PackageVersion "${pv.qualifiedVersionKey}" has `created` < 2011.';
      }
  
      yield* _checkPubspec(
          'PackageVersion', pv.qualifiedVersionKey.toString(), pv.pubspec!);
  
      _versionChecked++;
      if (_versionChecked % 5000 == 0) {
  
negative.code: 
    Future<bool> _packageMissing(String packageName) async =>
        !(await _packageExists(packageName));
  
    Stream<String> _reportPubspecVersionIssues() async* {
      for (final String package in _badVersionInPubspec.keys) {
        final values = _badVersionInPubspec[package]!.toList()..sort();
        // report the number of versions affected, plus the first 10 versions
        yield [
          'Bad version format in pubspec for package "$package" ${values.length} versions: ',
          '${values.take(10).map((s) => '"$s"').join(', ')}',
          if (values.length > 10) ' and more.'
        ].join();
      }
    }
  }
  