Mark System.Net.WebClient.Tests assembly with ActiveIssue

Author: MaximLipnin

src/libraries/System.Net.WebClient/tests/AssemblyInfo.cs

@@ -0,0 +1,7 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using Xunit;
+
+[assembly: ActiveIssue("https://github.com/dotnet/runtime/issues/34690", TestPlatforms.Windows, TargetFrameworkMonikers.Netcoreapp, TestRuntimes.Mono)]

src/libraries/System.Net.WebClient/tests/System.Net.WebClient.Tests.csproj

@@ -4,6 +4,7 @@
     <DefineConstants>$(DefineConstants);NETSTANDARD</DefineConstants>
   </PropertyGroup>
   <ItemGroup>
+    <Compile Include="AssemblyInfo.cs" />
     <Compile Include="WebClientTest.cs" />
     <Compile Include="$(CommonTestPath)System\Net\Capability.Security.cs">
       <Link>Common\System\Net\Capability.Security.cs</Link>