v0.4.2

This patch release 0.4.2 makes database lookups safe to embed.

• A lookup no longer creates or writes the database file, and a missing, damaged or locked database now raises DatabaseNotReadyError (CLI exit 2) instead of a raw sqlite3.Error.
• update no longer uses WAL mode, so lookups leave no -wal or -shm files.

What's changed

• Lookups never create or write the database by @bact in #80

Full Changelog: v0.4.1...v0.4.2