The .pyl files in src/testing/buildbot represent a database of which tests run on which machines. It would be helpful to be able to query this database rather than having to scan the generated .json files.

Queries which would be useful:

 - Which tests run on a particular bot
 - On which bots a particular test runs
 - Tests which contain a particular property (like 'should_retry_with_patch')

A "-q" or "--query" argument to generate_buildbot_json.py could handle all of these. It could auto-detect whether the argument is a bot, test, or property name/value. Optionally, it could output its results in JSON format for easier consumption by other tools.