Package manager in Visual Studio 2015 "407 (Proxy Authentication Required)"
<p><em>I understand this is an often asked question, however after days of research I've not found an answer to this particular problem.</em></p>

<hr>

<p>I have a new ASP.NET 5 (Core 1.0) MVC template that I'm trying to add a package to however each and every time I get in the Package Manager output:</p>

<pre><code>Response status code does not indicate success: 407 (Proxy Authentication Required). 
</code></pre>

<p>and the following at the top of solution explorer:</p>

<p><a href="https://i.stack.imgur.com/sMUaV.png" rel="noreferrer"><img src="https://i.stack.imgur.com/sMUaV.png" alt="enter image description here"></a></p>

<p>my settings look fine and I am able to browse packages in the 'Manage Packages for Solution' screen.</p>

<p>I understand I'm being requested to supply credentials so where do I enter them?  On the other hand all other applications on my machine have validated internet access, so why should I?</p>

<p>Any ideas / pointers are very welcome.</p>

<p><strong>Visual Studio 2015</strong> - 14.0.24720.00 Update 1 <br />
<strong>NuGet Package Manager for Visual Studio 2015</strong> - 3.3.0.167</p>

<hr>

<p>Top section of Package Manager output:</p>

<p>Installing NuGet package AutoMapper.4.2.1.<br />
Successfully installed 'AutoMapper 4.2.1' to CustomerPortal<br />
========== Finished ==========<br />
PATH=.\node_modules.bin;%PATH%;C:\Program Files (x86)\Microsoft Visual Studio 14.0\Common7\IDE\Extensions\Microsoft\Web Tools\External;C:\Program Files (x86)\Microsoft Visual Studio 14.0\Common7\IDE\Extensions\Microsoft\Web Tools\External\git<br />
C:\Users\medmondson.dnx\runtimes\dnx-clr-win-x86.1.0.0-rc1-update1\bin\dnx.exe "C:\Users\medmondson.dnx\runtimes\dnx-clr-win-x86.1.0.0-rc1-update1\bin\lib\Microsoft.Dnx.Tooling\Microsoft.Dnx.Tooling.dll" restore "M:\visual studio 2015\Projects\CustomerPortal\src\CustomerPortal" -f "C:\Program Files (x86)\Microsoft Web Tools\DNU"<br />
Microsoft .NET Development Utility Clr-x86-1.0.0-rc1-16231<br />
  GET <a href="https://www.nuget.org/api/v2/" rel="noreferrer">https://www.nuget.org/api/v2/</a><br />
  GET <a href="http://packages.nuget.org/v1/FeedService.svc/" rel="noreferrer">http://packages.nuget.org/v1/FeedService.svc/</a><br />
  GET <a href="https://www.postsharp.net/nuget/packages/" rel="noreferrer">https://www.postsharp.net/nuget/packages/</a><br />
Restoring packages for M:\visual studio 2015\Projects\CustomerPortal\src\CustomerPortal\project.json<br />
  GET <a href="https://www.nuget.org/api/v2/FindPackagesById()?id=" rel="noreferrer">https://www.nuget.org/api/v2/FindPackagesById()?id=</a>'AutoMapper'<br />
  GET <a href="http://packages.nuget.org/v1/FeedService.svc/FindPackagesById()?id=" rel="noreferrer">http://packages.nuget.org/v1/FeedService.svc/FindPackagesById()?id=</a>'AutoMapper'<br />
  GET <a href="https://www.postsharp.net/nuget/packages/FindPackagesById()?id=" rel="noreferrer">https://www.postsharp.net/nuget/packages/FindPackagesById()?id=</a>'AutoMapper'<br />
Warning: FindPackagesById: AutoMapper<br />
  An error occurred while sending the request.<br />
  GET <a href="https://www.nuget.org/api/v2/FindPackagesById()?id=" rel="noreferrer">https://www.nuget.org/api/v2/FindPackagesById()?id=</a>'AutoMapper'<br />
  GET <a href="https://www.nuget.org/api/v2/FindPackagesById()?id=" rel="noreferrer">https://www.nuget.org/api/v2/FindPackagesById()?id=</a>'System.Collections.Immutable'<br />
  GET <a href="http://packages.nuget.org/v1/FeedService.svc/FindPackagesById()?id=" rel="noreferrer">http://packages.nuget.org/v1/FeedService.svc/FindPackagesById()?id=</a>'System.Collections.Immutable'<br />
  GET <a href="https://www.postsharp.net/nuget/packages/FindPackagesById()?id=" rel="noreferrer">https://www.postsharp.net/nuget/packages/FindPackagesById()?id=</a>'System.Collections.Immutable'<br />
Warning: FindPackagesById: AutoMapper<br />
  An error occurred while sending the request.<br />
  GET <a href="https://www.postsharp.net/nuget/packages/FindPackagesById()?id=" rel="noreferrer">https://www.postsharp.net/nuget/packages/FindPackagesById()?id=</a>'AutoMapper'<br />
Warning: FindPackagesById: AutoMapper<br />
  Response status code does not indicate success: 407 (Proxy Authentication Required).<br /></p>

<h1>Update</h1>

<p>I've managed to capture a non-working request (returning 407) and a working request with the <strong>only difference being the content of the Proxy-Authorization header</strong> which is longer.  This would suggest the proxy authentication does exist but it's using a different protocol.</p>