Fix bug in pycsw: random errors when using dev-elodief branch

[ElodieFZ]

The dev-elodief branch contains the modification from #237 (Adding new queryables).

It seems to work fine: when running a pycsw container, the indexed xml files are rendered as expected, with the new fields (data center, ...). But when the branch is deployed in a full test environment ( https://testing.met.no/ ), when one makes a query, it sometimes works, and sometimes returns an internal server error. This does not happen on the end points using the other pycsw branches.

To do:

• compare dev-met and dev-elodief
• isolate changes
• set up new end points as needed to check if internal errors still happen

[ElodieFZ]

The internal server errors were not related to the code updates but to the pycsw db. It needs to be optimized when it reaches a large size. Tuning of the db is now enabled in the pycsw admin command: [https://github.com/geopython/pycsw/pull/678]()