PathNotFoundException: Cannot open file - pubspec.lock

When using Pub workspaces for monorepos, pubspec.lock is not generated in packages.

So, the following handling is needed.

```dart
final pubspecLockFile = File('$currentPath/pubspec.lock');
if (pubspecLockFile.existsSync()) {
  final pubspecLock = loadYaml(pubspecLockFile.readAsStringSync());
  dependencies.addAll(pubspecLock['packages'].keys);
}
```