cli/create_db: return an erroneous exit on on error

lib/cli/commands/create_db.dart

@@ -35,12 +35,19 @@ class CreateDb extends Command {
       readWrite: true,
     );
 
+    bool failed = false;
     await seedData(db).then((_) {
       print("Database created successfully");
     }).catchError((error) {
       print("Error creating database: $error");
+      failed = true;
     }).whenComplete(() {
       db.close();
     });
+    if (failed) {
+      exit(1);
+    } else {
+      exit(0);
+    }
   }
 }