Add a test for USERD case file reader

[randallfrank]

Read the xml crash dataset using libuserd.

[kecolburn]

I did not see immediately that this forced the use of the VKI reader. I assume that the libuserd doesn't know about the EnSight Case format, and those only finds this VKI reader for the query on the .case file. From an user perspective, are they fooled a bit by thinking this is an EnSight Case Gold reader, while it is actually a VKI reader (which may / may not work completely).

[randallfrank]

I did not see immediately that this forced the use of the VKI reader. I assume that the libuserd doesn't know about the EnSight Case format, and those only finds this VKI reader for the query on the .case file. From an user perspective, are they fooled a bit by thinking this is an EnSight Case Gold reader, while it is actually a VKI reader (which may / may not work completely).

@kecolburn exactly. The VKI EnSight case gold reader is named "USERD EnSight Case" and is the only userd reader that can reader .case files. So:

readers = libuserd.query_format("example.case")
assert len(readers) == 1
assert readers[0].name == "USERD EnSight Case"

verifies that there is one and only reader .case file reader and that the name of the reader matches the VKI reader name. From a user's perspective, we have a reader than can read (a subset of) the casefile format. In the future, we can replace the VKI implementation with something else that might be more capable and we would replace the implementation of that reader, but keep the name.

My approach for finding the file is broken for docker however, so another commit is inbound.