Start-BitsTransfer cannot be leveraged in some instances

[nickhorvath]

in Install-UnitySetupInstance
the line
Start-BitsTransfer -Source $downloadSource -Destination $downloadDest

fails if it's executed from a Visual Studio Team Services build agent with as the VSTS Agent runs as a service.
2018-08-03T17:31:03.2273217Z DEBUG: 472+ >>>> Start-BitsTransfer -Source $downloadSource -Destination $downloadDest
2018-08-03T17:31:03.7159554Z Start-BitsTransfer : The operation being requested was not performed because the user has not logged on to the
2018-08-03T17:31:03.7159834Z network. The specified service does not exist. (Exception from HRESULT: 0x800704DD)
2018-08-03T17:31:03.7160174Z At C:\Program Files\WindowsPowerShell\Modules\UnitySetup\4.0.97\UnitySetup.psm1:472 char:13

Either credentials need to be supplied to the call (and piped through as params) or it should use webclient to download the installer
(New-Object System.Net.WebClient).DownloadFile([string]$downloadSource, [string]$downloadDest)

I'm testing this E2E now.

[nickhorvath]

Confirmed that (New-Object System.Net.WebClient).DownloadFile([string]$downloadSource, [string]$downloadDest) passes without issue. can submit a PR if needed.

[Ziugy]

I found that Start-BitsTransfer is also not currently available on macOS. I think it would be great if you could get a PR up with WebClient, though I would prefer we keep bits as the default and have WebClient as the fallback. Bits transfers much faster, if available.

[shrinktofit]

Still not available on macOS.