Fix analysis hints (#450)

lib/src/executable/watch.dart

@@ -117,7 +117,6 @@ class _Watcher {
   ///
   /// Returns a future that will only complete if an unexpected error occurs.
   Future watch(MultiDirWatcher watcher) async {
-    loop:
     await for (var event in _debounceEvents(watcher.events)) {
       var extension = p.extension(event.path);
       if (extension != '.sass' && extension != '.scss') continue;

test/cli/shared.dart

@@ -3,7 +3,6 @@
 // https://opensource.org/licenses/MIT.
 
 import 'dart:async';
-import 'dart:io';
 
 import 'package:path/path.dart' as p;
 import 'package:test/test.dart';