Keep a config filename variable; make sure the file is promptly closed
Keep a config filename variable; make sure the file is promptly closed

It's useful to use the config filename in errors (e.g. in
the subsequent commit).  The other change is use the with
statement for opening the config file to ensure that the
file is closed immediately.

opencorato/sayit,opencorato/sayit,opencorato/sayit,opencorato/sayit