Failed to build intl_utils:generate:
../../../.pub-cache/hosted/pub.flutter-io.cn/watcher-1.0.2/lib/src/constructable_file_system_event.dart:7:57: Error: The class 'FileSystemEvent' can't be extended, implemented, or mixed in outside of its library because it's a sealed class.
abstract class _ConstructableFileSystemEvent implements FileSystemEvent {
解决办法：
请尝试 dart pub upgrade 命令，如果还是报错 dart pub cache repair ，这样我们就可以使用到最新的watcher-1.1.0版本，就不会出现上面这个报错了
如果出现：Could not find bin/generate.dart in package intl_utils 可能是版本不对 升级版本
