John Parejko will you please take a look at these changes? They are what were needed to add VisitInfo to the calexp when using processEimage.

Reviewed. My main problem is the lack of a test. Unless this is tested by existing code (which would very much surprise me), I'd like a test for it. Of course, if there isn't a test of raw VisitInfo lsstSim stuff or if we don't have eimage files in testdata_lsstSim, then that may be hard to do.

There is no eimage in obs_test. Is it reasonable to put a test of VisitInfo in obs_base? The problem is that we don't have a testdata_lsstSim package. What do you suggest?

Per our discussion earlier, there is a data/ directory in tests where you could add an eimage to test against. Please note in the unittest that this is an lsstSim-specific test (e.g. it shouldn't get lifted into obs_base).

I added a unit test. Can you have a look? The jenkins build passes on py2 (#17666).

A few remaining comments, but otherwise looks good to merge.