Microsoft has changed the way to restore NuGet packages inside Visual Studio Team Services (VSTS). It was previously done inside the Visual Studio Build task shown below.
If you hover over the Information icon, a new message is now displayed.
Microsoft has not set a date when this option will become obsolete. This can cause a potential problem for projects using custom or private NuGet packages. Also, this differs from how NuGet is run inside Visual Studio.
They recommend using the new task called "NuGet Installer"
There are options such as path to the ".sln" and the "nuget.config" file.
With these options, a developer can use a custom NuGet configuration file to point to a private repository or local file path along with custom arguments not supported with the traditional task parameters.
I was trying to merge my latest project over to this new task, but ran into an issue. I was using a relative, not absolute, path to point to a local NuGet package that is checked into source control. Here is the GitHub Issue that was unfortunately closed :( . I will be sticking with the NuGet Restore inside the build for now.