Added NuGet packages, now Android app won't run due to missing System.Diagnostics.Tracing

I'm not referencing System.Diagnostics.Tracing anywhere. Perhaps one of the NuGet packages I just installed do, but as far as I can tell they don't. Anyway, after installing the packages below and running the (otherwise largely untouched) hello world app, I get this error:

<package id="IronPigeon" version="0.3.2-preview" targetFramework="MonoAndroid403" />
<package id="IronPigeon.Dart" version="0.3.2-preview" targetFramework="MonoAndroid403" />
<package id="Microsoft.Bcl" version="1.1.6" targetFramework="MonoAndroid403" />
<package id="Microsoft.Bcl.Build" version="1.0.13" targetFramework="MonoAndroid403" />
<package id="Microsoft.Composition" version="1.0.20" targetFramework="MonoAndroid403" />
<package id="Microsoft.Net.Http" version="2.2.18" targetFramework="MonoAndroid403" />
<package id="Microsoft.Tpl.Dataflow" version="4.5.14" targetFramework="MonoAndroid403" />
<package id="Validation" version="2.0.3.13323" targetFramework="MonoAndroid403" />

1>C:\Program Files (x86)\MSBuild\Xamarin\Android\Xamarin.Android.Common.targets(853,2): error : Exception while loading assemblies: System.IO.FileNotFoundException: Could not load assembly 'System.Diagnostics.Tracing, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a'. Perhaps it doesn't exist in the Mono for Android profile? File name: 'System.Diagnostics.Tracing.dll' at Xamarin.Android.Tuner.DirectoryAssemblyResolver.Resolve(AssemblyNameReference reference, ReaderParameters parameters) at Xamarin.Android.Tasks.ResolveAssemblies.AddAssemblyReferences(List`1 assemblies, AssemblyDefinition assembly, Boolean topLevel) at Xamarin.Android.Tasks.ResolveAssemblies.Execute()