Bootcamp does not writing Windows 10 support software to USB flash
El Capitan 10.11.4 / iMac 27" late 2013 / Bootcamp 6.0.1 says that it cannot install the Windows support files to the USB flash as required to create an external USB Windows 10 bootable device.
Using a full Windows 10 clean copy downloaded used , an ISO file.
Help highly appreciated.
iMac (27-inch, Late 2013), OS X El Capitan (10.11.4), null