The F06 reader is no longer distributed with the release versions of pyNastran (at least for now). It's a much harder file to parse, it's slower, it supports fewer results, and there are no major results that it has that the OP2 reader does not have that the F06 reader supports. The F06 reader doesn't support max ratio/oloads. While you won't get the error message, the OP2 does determine if there was a FATAL.
All you need to make an OP2 is add:
$ -2 will also work
to the BDF
If you're after results (e.g. static/transient displacement, spc forces, mpc forces, applied loads, stress, force, strain energy, grid point forces, weight, eigenvalues, eigenvectors), then the OP2 can read it. It supports multiple subcases, superelements while being 100x faster.