IPSW creation failed!

It seems this issue is being caused by an old plugin from the 'Virtual PC' application. Yes, your heard right Virtual PC - the Windows virtualization app from the PPC days. 

The fix is to simply remove the 'VirtualPCDiskImagePlugin.bundle' which can be found in one of two places:

~/Library/Plug-ins/DiskImages
/Library/Plug-ins/DiskImages

After removing the plugin restart your computer and re-run Seas0nPass.