If the application's installer exit code is a success, and the user has a pre or post script define, please consider allowing PatchMyPC-ScriptRunner.exe to exit with exit code of the pre or post script. It might be ideal for an admin to fail the install of an app or update if a pre or post script fails.
Perhaps this behaviour could be controlled via a checkbox in the Add custom pre/post script dialogue where the default behaviour is how it is today (not to use the pre/post script exit code, only the installer's) and enabling the checkbox would enable this new proposed functionality.
Perhaps the checkbox could be worded as "Use script exit code if installation is successful"