我尝试使用 'pub get' 安装聚合物飞镖博客的依赖项，但不幸的是此操作失败。我完全不知道问题是什么。输出如下所示：
C:\Users\fraherm\workspace\polymer-dart-blog>pub get
Resolving dependencies..........................................................
................................................................................
................................................................................
................................................................Error in PubHttp
Client.send (issue 12581) error: HttpException: Connection closed before full he
ader was received, uri = https://pub.dartlang.org/api/packages/unittest/versions
/0.8.10%2B3
stacktrace: #0 PubHttpClient.send (file:///e:/b/build/slave/dart-editor
-win-stable/build/dart/sdk/lib/_internal/pub/lib/src/http.dart:60)
#1 BaseClient._sendUnstreamed.<anonymous closure> (package:http/src/base_cl
ient.dart:118)
#2 _Future._propagateToListeners.<anonymous closure> (dart:async/future_imp
l.dart:453)
#3 _rootRun (dart:async/zone.dart:683)
#4 _RootZone.run (dart:async/zone.dart:823)
#5 _Future._propagateToListeners (dart:async/future_impl.dart:445)
#6 _Future._complete (dart:async/future_impl.dart:303)
#7 _Future._asyncComplete.<anonymous closure> (dart:async/future_impl.dart:
354)
#8 _asyncRunCallback (dart:async/schedule_microtask.dart:18)
#9 _createTimer.<anonymous closure> (dart:async-patch/timer_patch.dart:11)
#10 _Timer._createTimerHandler._handleTimeout (timer_impl.dart:151)
#11 _Timer._createTimerHandler.<anonymous closure> (timer_impl.dart:166)
#12 _RawReceivePortImpl._handler (dart:isolate-patch/isolate_patch.dart:1)
#13 _RawReceivePortImpl._handleMessage (dart:isolate-patch/isolate_patch.dar
t:93)
Connection closed before full header was received