VS30063: You are not authorized to access

So. I've just installed Visual Studio 2015 Update 3 (VS2015.3) and I'm getting this in the output window at startup:

We were unable to automatically populate your Visual Studio Team Services accounts. The following error was encountered:
VS30063: You are not authorized to access https://app.vssps.visualstudio.com.

What I had to was re-login.

In the top right corner of Visual Studio, I found a yellow warning triangle next to the place for my name. I clicked the down arrow and then the "Relogin" message.

After I restarted Visual Studio and signed back in, the error was gone.

Could not load file or assembly 'Microsoft.CodeAnalysis, version= 1.3.1.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35' or one of its dependencies

I can't get the light bulb in Visual Studio 2015, and when I go to the context menu, I now get an error message:

Could not load file or assembly 'Microsoft.CodeAnalysis, version= 1.3.1.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35' or one of its dependencies. The system cannot find the file specified.

So, for me, the answer was to install Visual Studio Update 3, found in Visual Studio under
Tools >> Extensions and Updates...