Detect and overwrite corrupt PEP 514 registry entries #11
Description
The old MSI installer sometimes doesn't clean up the registry properly on uninstall, leaving keys behind. We will detect this and refuse to write new entries there, and also print a warning to users.
However, if the key doesn't contain an InstallPath subkey, it's almost certainly not usable. So rather than complain, we should clean up after our predecessor and write it with the new install.