lxd/db/schema/schema.go
func checkSchemaVersionsHaveNoHoles(versions []int) error {
	// Sanity check that there are no "holes" in the recorded
	// versions.
	for i := range versions[:len(versions)-1] {
		if versions[i+1] != versions[i]+1 {
			return fmt.Errorf("Missing updates: %d to %d", versions[i], versions[i+1])
		}
	}
	return nil
}
func checkSchemaVersionsHaveNoHoles(versions []int) error {
	// Sanity check that there are no "holes" in the recorded
	// versions.
	for i := range versions[:len(versions)-1] {
		if versions[i+1] != versions[i]+1 {
			return fmt.Errorf("Missing updates: %d to %d", versions[i], versions[i+1])
		}
	}
	return nil
}
// Check that the given list of update version numbers doesn't have "holes",
// that is each version equal the preceding version plus 1.