unity打包报错，目标文件夹是空的，报错代码如下：
InvalidOperationException: Certificate Assets\WSATestCertificate.pfx is expired and cannot be used for a UWP build. To fix this, either delete it or select a different certificate in the player settings.
PostProcessWinRT.CreateTestCertificate () (at C:/buildslave/unity/build/PlatformDependent/MetroPlayer/Extensions/Managed/PostProcessWinRT.cs:1078)
PostProcessWinRT.Process () (at C:/buildslave/unity/build/PlatformDependent/MetroPlayer/Extensions/Managed/PostProcessWinRT.cs:168)
UnityEditor.UWP.BuildPostprocessor.PostProcess (UnityEditor.Modules.BuildPostProcessArgs args) (at C:/buildslave/unity/build/PlatformDependent/MetroPlayer/Extensions/Managed/ExtensionModule.cs:86)
Rethrow as BuildFailedException: Exception of type ‘UnityEditor.Build.BuildFailedException’ was thrown.
分析以后应该是这个项目的WSA证书过期了。解决办法：
在Unity工具栏中找到 File -> Build Settings。
选择 Windows -> Universal Windows Platform
点击左下角 Player Settings。打开下面这个界面
在 Player Settings 窗口中，找到 Publishing Settings。
在 certificate 部分，删除替换过期的 WSATestCertificate.pfx 证书。
生成新的测试证书：
点击 Create Test Certificate 来生成一个新的证书。
这样就可以正常编译程序了