CI 3.X Session Core problems

Having both classes declare that they implement the same interface can be construed as being explicit. It is *not* any sort of fatal error.

Read the error message: PHP cannot find your error view files.

It looks more likely that you upgraded from CI2 to CI3 without updating your application folder. CI2 had application/errors, whereas CI3 has application/views/errors.

I feel like you're right, but I'm upgrading from 3.1.0 to 3.1.8, I don't think you're saying that.