your error message will have to be a bit more descriptive: when user is useing nwchem, and wants to try out a new version, it will trigger this error. i'd add something like ```Please temporarily rename the self.home_nwchemrc during nwchem installation. It can be restored later for nwchem use```.
Btw, we should cleanup the self.home_nwchemrc after installation (and to be on the safe side, also their i'd check if samefile(self.home_nwchemrc, self.local_nwchemrc)), so a user can simple rename the original home_nwchemrc