PowerShell cmdlet Push-AppveyorArtifact not available any more after latest Ubuntu image update

[bergmeister]

See here for an example build failure introduced by the latest Ubuntu image update in the last days

[JustArchi]

ref: #2183 (comment)

[Wasapl]

Fixed. @bergmeister Can you please verify that your build works fine.

[bergmeister]

@Wasapl Awesome, yes it is fixed now. Thanks. Amazing support :-)