The source at nuget.org [https://www.nuget.org/api/v2/] is unreachable. Falling back to NuGet Local Cache

I started getting the following error while trying to use Install-Package:

The source at nuget.org [https://www.nuget.org/api/v2/] is unreachable. Falling back to NuGet Local Cache

It was driving me insane as it started out being intermittent and restarting Visual Studio would fix it for a while.  Finally did some googling and turns out you can specify a -Source parameter like so:

Install-Package AutoMapper -Source nuget.org

This worked for me.