Oracle: not raising exceptions from DatabaseOperations.execute breaks Oracle backend

[Sam Hartsfield <samh.public@…>]

The Oracle backend's DatabaseOperations?.alter_column depends on catching and checking exceptions thrown by DatabaseOperations?.execute, but changeset 0918d7a8e8395370529e9ace222e6f546d860d3f breaks this by printing the error and not re-raising.

Could these kinds of errors maybe be caught at a higher level, that is, print and exit only if the backend doesn't handle it? Maybe in Migrator.run_migration?