I'm not sure if this is a potential bug or something missing in the upgrade instructions or what, but I went through the upgrade instructions, fixed all my conf files, etc but was having an issue when a student clicks on a problem set. Basically it said could not read file /opt/webwork/webwork2/conf/snippets/ASimpleCombinedHeadrFile.pg. When I checked the conf directory had no snippets subdirectory. I saved off my original conf directory before upgrading and it was there, so I copied it back and then it was fine. But as I said, I'm not sure if that was the right thing to do, or if this a potential bug. If it is a bug I'm happy to open a ticket
This is not a bug. There should be no conf/snippets directory. That is no longer used by webwork2. Check your localOverrides.conf and site.conf files carefully. You must still have a reference to that directory somewhere, and that is why you are getting that error.