Sqlite3.RcSourceType of unknown return codes
int_of_unknown n converts unknown return code rc to an integer.
type t = | OK| ERROR| INTERNAL| PERM| ABORT| BUSY| LOCKED| NOMEM| READONLY| INTERRUPT| IOERR| CORRUPT| NOTFOUND| FULL| CANTOPEN| PROTOCOL| EMPTY| SCHEMA| TOOBIG| CONSTRAINT| MISMATCH| MISUSE| NOFLS| AUTH| FORMAT| RANGE| NOTADB| ROW| DONE| UNKNOWN of unknownType of return codes from failed or successful operations.
check rc raises an exception if rc does not correspond to a return code indicating success.