CHANGES.txt: add HDFS-7419

hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt

@@ -390,6 +390,9 @@ Release 2.7.0 - UNRELEASED
 
     HDFS-7412. Move RetryCache to NameNodeRpcServer. (wheat9)
 
+    HDFS-7419. Improve error messages for DataNode hot swap drive feature (Lei
+    Xu via Colin P. Mccabe)
+
   OPTIMIZATIONS
 
   BUG FIXES