I ran into this while helping Rolf diagnose some nuget feed issues in the macios build.
If you redirect stdout of nuget, then it basically never finishes and writes an endless stream of 12spaces+linefeed.
Repro: Run "nuget help > test.log"
It seems to happen on all nuget commands, except (interestingly) on "nuget restore".
Similar report on the nuget bug tracker: https://github.com/NuGet/Home/issues/2029
I'm not 100% sure if it's a nuget or Mono problem, but given that redirecting stdout works on Windows it's likely the latter.