Create Logger backend

[rabidpraxis]

We had a request for logging errors during test runs. Per this conversation (via @ioquatix):

https://twitter.com/ioquatix/status/1318312887547408384

One way we could solve this is to add another backend option, perhaps a Logger backend. Instead of reporting on the notify method, we can log the error to stderr. We should also log the check_in id as well.