storage: Surface "already exists" errors.

storage/sql/migrate_test.go

@@ -6,6 +6,7 @@ import (
 	"testing"
 
 	"github.com/Sirupsen/logrus"
+	sqlite3 "github.com/mattn/go-sqlite3"
 )
 
 func TestMigrate(t *testing.T) {
@@ -21,7 +22,15 @@ func TestMigrate(t *testing.T) {
 		Level:     logrus.DebugLevel,
 	}
 
-	c := &conn{db, flavorSQLite3, logger}
+	errCheck := func(err error) bool {
+		sqlErr, ok := err.(sqlite3.Error)
+		if !ok {
+			return false
+		}
+		return sqlErr.ExtendedCode == sqlite3.ErrConstraintUnique
+	}
+
+	c := &conn{db, flavorSQLite3, logger, errCheck}
 	for _, want := range []int{len(migrations), 0} {
 		got, err := c.migrate()
 		if err != nil {