If Unreal 4 reports back with the following error, don’t freak out.
LogWindows:Error: Windows GetLastError: The operation completed successfully. (0)
This means that you have likely copied or refactored some code, resulting in duplicated code. This does not mean that you screwed up, it could have just been Perforce or Git screwing with you. Do a quick sanity check and make sure that you have your code laid out appropriately and you should be cooking with gas.