In its simplest configuration, `sqla-raw` gets a `$DATABASE_URL` from the local execution environment, and uses that as default connection string. In previous versions, the call to `os.getenv()` included in-memory SQLite database (`sqlite:///`) as a fallback default, in case the environment variable was not defined. This seemed handy and made some testing scenarios easier to provision, but could lead to confusing error messages in practice: an operator who hadn't realized that `$DATABASE_URL` was set to an expected `postgresql://...` value might be quite surprised to get SQLite syntax error exceptions when submitting SQL that's valid for Postgres but not supported in SQLite -- especially in the context of a larger program using `sqla-raw` as a library.
Better to have no default, and raise an exception specifically complaining that no database URL was specified when that's the case. That's the implementation from this release forward.
Calling this a minor update since the SQLite default was undocumented, it doesn't change the existing API meaningfully, and I doubt anyone is currently using it in a way that relies on the old default behavior.