As we use locks more, we may hit this again.
The recent changes to styles.php mean that we attempt to get a lock during install.

Unless a specific lock factory is set in config, the default is:

• Try and fetch a lock factory for the current database
  • if it does not exist, then use the file lock factory;
  • if it does exist, but is not available, fall back to generic db_record locking.

Consider the following scenarios:

Since postgres does have a DB-specific factory, if it is somehow not available (not possible with the way the code is called), the fallback would be a generic DB factory.

To solve this issue the obvious thing to do is to use the file_lock_factory during initial install.
However, I wonder whether we should be standardising the fallback so that if the DB-specific factory returns as being unavailable, we always use the same file_lock_factory, or whether we should switch all other Ds to use the db_record_lock_factory instead.

Possibly this should be a different issue.