Release file does not exist
Solution 1:
The 404 error suggests there are no package candidates on that repository for ubuntu xenial. That is because the ppa does not exist for xenial (16.04), as you can see here. The latest packages available corresponds to 15.04 (vivid). It seems that the PPA for WinUSB is no longer being maintained by its author. Follow these instructions to install WinUSB on 16.04. Also, check this answer for an alternative method to WinUSB.
For workaround, you can simply removing the ppa:
sudo add-apt-repository -r ppa:colingille/freshlight
sudo apt update