4.3 Failed to Cook for Launch

Before the 4.3 release for UE4 my project would Cook / Package and Launch perfectly fine, however once updating the engine through the official Unreal Engine Launcher it will no longer Cook properly. It is a purely Blueprint based project.

LogPlayLevel:Display: CommandUtils.Run: Run: Took 29.7587021s to run UE4Editor-Cmd.exe
LogPlayLevel:Display: Project.Cook: Cook failed. Deleting cooked data.
LogPlayLevel:Display: BuildCommand.Execute: ERROR: BUILD FAILED
LogPlayLevel:Display: Program.Main: ERROR: AutomationTool terminated with exception:
LogPlayLevel:Display: Program.Main: ERROR: Exception in AutomationScripts.Automation: BUILD FAILED: Failed while running Cook for C:\Users\user\Documents\Unreal Projects\ProjectBlueprint\ProjectBlueprint.uproject; see log C:\Program Files\Unreal Engine\4.3\Engine\Programs\AutomationTool\Saved\Logs\Cook.txt
LogPlayLevel:Display: Stacktrace: at Project.Cook(ProjectParams Params)
LogPlayLevel:Display: at BuildCookRun.DoBuildCookRun(ProjectParams Params)
LogPlayLevel:Display: at BuildCommand.Execute()
LogPlayLevel:Display: at AutomationTool.Automation.Execute(List1 CommandsToExecute, CaselessDictionary1 Commands)
LogPlayLevel:Display: at AutomationTool.Automation.Process(String[] CommandLine)
LogPlayLevel:Display: at AutomationTool.Program.MainProc(Object Param)
LogPlayLevel:Display: at AutomationTool.InternalUtils.RunSingleInstance(MainProc Main, Object Param)
LogPlayLevel:Display: at AutomationTool.Program.Main()
LogPlayLevel:Display: Program.Main: ERROR: BUILD FAILED: Failed while running Cook for C:\Users\user\Documents\Unreal Projects\ProjectBlueprint\ProjectBlueprint.uproject; see log C:\Program Files\Unreal Engine\4.3\Engine\Programs\AutomationTool\Saved\Logs\Cook.txt
LogPlayLevel:Display: ProcessManager.KillAll: Trying to kill 0 spawned processes.
LogPlayLevel:Display: Program.Main: AutomationTool exiting with ExitCode=1
LogPlayLevel:Display: Domain_ProcessExit
LogPlayLevel:Display: ProcessManager.KillAll: Trying to kill 0 spawned processes.
LogPlayLevel:Display: copying UAT log files…
LogPlayLevel:Display: RunUAT.bat ERROR: AutomationTool was unable to run successfully.
LogPlayLevel:Display: BUILD FAILED

Similar problems here, maybe this helps:

https://answers.unrealengine.com/questions/75918/packaging-failed-ue-430.html

Hello,

Thank you for your report. We were not able to investigate this on the engine version you reported, but there have been many version changes to UE4 since this question was first posted. With a new version of the Engine comes new fixes and it is possible that this issue has changed or may no longer occur. Due to timetable of when this issue was first posted, we are marking this post as resolved for tracking purposes. If you are still experiencing the issue you reported in the current engine version, then please respond to this message with additional information and we will investigate as soon as possible. If you are experiencing a similar, but different issue at this time, could you please submit a new report for it.

Thanks!