When in multi show a nice error if not using TransactionJedis

src/test/java/redis/clients/jedis/tests/commands/TransactionCommandsTest.java

@@ -8,6 +8,7 @@ import java.util.List;
 import org.junit.Test;
 
 import redis.clients.jedis.Jedis;
+import redis.clients.jedis.JedisException;
 import redis.clients.jedis.Transaction;
 import redis.clients.jedis.TransactionBlock;
 
@@ -94,4 +95,10 @@ public class TransactionCommandsTest extends JedisCommandTestBase {
 	expected.add("OK");
 	assertEquals(expected, resp);
     }
+
+    @Test(expected = JedisException.class)
+    public void validateWhenInMulti() {
+	jedis.multi();
+	jedis.ping();
+    }
 }