title: Invalid .nuspec file: target framework `Unsupported,Version=v0.0` is not supported
body: <p>So embarrassing to ask something that is that well documented, but I am lost with an error which I get when I push my NuGet package:</p>
  
  <p><a href="https://i.stack.imgur.com/iwVq9.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/iwVq9.png" alt="enter image description here"></a></p>
  
  <blockquote>
    <p>System.AggregateException: One or more errors occurred. --->
    System.Net.Http.HttpRequestException: Response status code does not
    indicate success: 400 (The NuGet package contains an <strong>invalid .nuspec
    file</strong>. The error encountered was: 'The target framework
    <strong>Unsupported,Version=v0.0</strong> is not supported.'. Correct the error and try again.).</p>
  </blockquote>
  
  <p>I use the VSTS <em>NuGet</em> task to push the package to NuGet.org which delivers the aforesaid error. There's nothing customized, just the default settings:</p>
  
  <p>In my nuspec file I have listed dependencies, simplified example:</p>
  
  <pre><code>&lt;dependencies&gt;
    &lt;group targetFramework="netcoreapp"&gt;
      &lt;dependency id="Microsoft.NETCore.App" version="2.0.0" exclude="Build,Analyzers" /&gt;
    &lt;/group&gt;
    &lt;group targetFramework="net462" /&gt;
    &lt;group targetFramework="netstandard1.0" /&gt;
  &lt;/dependencies&gt;
  </code></pre>
  
  <p>I assume my <code>targetFramework</code> is set incorrectly yet it is as per documentation <a href="https://docs.microsoft.com/en-us/nuget/schema/target-frameworks" rel="nofollow noreferrer">NuGet Target Frameworks</a>. I tried target frameworks like <code>netstandard</code> and <code>netcoreapp2.0</code>, they all cause the same problem.</p>
  
  <p>My package files:</p>
  
  <pre><code>&lt;files&gt;
    &lt;file src="bin\MINE.Core.dll" target="lib\netcoreapp\MINE.Core.dll" /&gt;
    &lt;file src="bin\MINE.Core.NetFX.dll" target="lib\net462\MINE.Core.NetFX.dll" /&gt;
    &lt;file src="bin\MINE.Core.PCL.dll" target="lib\netstandard1.0\MINE.Core.PCL.dll" /&gt;
    &lt;file src="readme.core.txt" target="" /&gt;
  &lt;/files&gt;
  </code></pre>
  
  <p>If I leave the <code>dependencies</code> section empty (<code>&lt;dependencies /&gt;</code>) everything works perfectly fine except for the package doesn't list the dependencies which I'd like to include. Also, If I don't use groups and therefore don't target frameworks, but list all dependent packages, everything works fine.</p>
  
  <p>Any hint to solve this (probably silly) issue would be warmly appreciated.</p>