title: Visual Studio 2017 RC installation failure "product ... cannot be found"
body: <p>I am trying to install Visual Studio Professional 2017 RC on Windows 10 but the installer reports:</p>
  
  <pre><code>A product matching the following parameters cannot be found:
  
  channelId: VisualStudio.15.Release
  productId: Microsoft.VisualStudio.Product.Professional
  </code></pre>
  
  <p>Is this fixable?</p>