`smt upgrade` assumes the record store database is within the ".smt" directory
If the SQLite database file is elsewhere, then either there will be
django.db.utils.DatabaseError: no such column errors, or, in the absence of schema changes, there will be a risk of corruption, as multiple records with the same name could be created.
The solution for the SQLite backend is to delete the database file as well as deleting ".smt" (after making a backup copy, of course).
For the PostgreSQL backend, I guess we could either drop then recreate the tables, or use something like South to perform the schema migration.