Nuget repository only looks at Microsoft repository

Recently few things changed in Nuget word. Currently when I run:

get-packages -ListAvailable

It only shows packages from Microsoft.
To be able to use Nuget repo again and be able to install typical libriaries like NUnit one has to add NuGet.Config to a folder that holds the solution file.

<?xml version="1.0" encoding="utf-8"?>
<configuration>
  <packageSources>
    <add key="NuGet official package source" value="https://nuget.org/api/v2/" />
    <add key="local" value="C:\development\PathToYourLocalNugetRepositoryIfYouNeedIt\NugetLocal" />
  </packageSources>
</configuration>

After modification, Manage NuGet Packages tool should show All, NuGet official package source, local, Microsoft and .NET.