Building UE4 from source [error MSB3073 The command "..\..\Build\BatchFiles\Build.bat DatasmithSDK ...." exited with code 6

Now, if I go back to visual studio and instead of looking at the Error List tab (which only gives me a very short and obscure message

error MSB3073 The command "..\..\Build\BatchFiles\Build.bat DatasmithSDK blabla" exited with code 6. 

I should have went straight to the detailed errors in the Output tab where it shows: