I am using Visual Studio Online - Package Manager Preview, along with the new build system. The package manager preview adds a number of build steps, including a \"NuGet Pub
UPDATE: It is all fixed now so you can use the standard packaging steps in vNext and they work like a charm.
For the time being, I am substituting the NuGet Publisher step with a PowerShell build step.
This slots into the build after the "NuGet Packager" step and allows me to specify all of the credentials by setting up a package source before pusing the package.
$feedUrl = "https://example.pkgs.visualstudio.com/DefaultCollection/_packaging/Example/nuget/v3/index.json"
$packagePath = $ENV:BUILD_REPOSITORY_LOCALPATH + "\YourOrg.YourComponent." + $ENV:BUILD_BUILDNUMBER + ".nupkg"
Write-Host "Adding package Source"
$addSourceCommand = $ENV:BUILD_REPOSITORY_LOCALPATH + "\nuget sources add -name ""Example"" -source " + $feedUrl + " -username ""your.username"" -password ""yourpassword"""
Invoke-Expression -Command $addSourceCommand
Write-Host "Pushing package to NuGet"
$pushCommand = $ENV:BUILD_REPOSITORY_LOCALPATH + "\nuget push $packagePath -Source " + $feedUrl + " -ApiKey Example"
Invoke-Expression -Command $pushCommand