Add NotImplementedYetException for binary compatibility changes.

codec-http2/src/main/java/io/netty/handler/codec/http2/AbstractHttp2StreamFrame.java

@@ -15,6 +15,7 @@
  */
 package io.netty.handler.codec.http2;
 
+import io.netty.util.NotImplementedYetException;
 import io.netty.util.internal.UnstableApi;
 
 /**
@@ -36,6 +37,11 @@ public Http2FrameStream stream() {
         return stream;
     }
 
+    @Override
+    public byte frameType() {
+        throw new NotImplementedYetException();
+    }
+
     /**
      * Returns {@code true} if {@code o} has equal {@code stream} to this object.
      */

common/src/main/java/io/netty/util/NotImplementedYetException.java

@@ -0,0 +1,27 @@
+/*
+ * Copyright 2020 The Netty Project
+ *
+ * The Netty Project licenses this file to you under the Apache License,
+ * version 2.0 (the "License"); you may not use this file except in compliance
+ * with the License. You may obtain a copy of the License at:
+ *
+ *   https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations
+ * under the License.
+ */
+
+package io.netty.util;
+
+public final class NotImplementedYetException extends RuntimeException {
+    public NotImplementedYetException(String message) {
+        super(message);
+    }
+
+    public NotImplementedYetException() {
+        super("Not implemented yet.");
+    }
+}