HDFS-6028. Print clearer error message when user attempts to delete required mask entry from ACL. Contributed by Chris Nauroth.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/trunk@1572753 13f79535-47bb-0310-9956-ffa450edef68

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

@@ -642,6 +642,9 @@ Release 2.4.0 - UNRELEASED
     HDFS-5908. Change AclFeature to capture list of ACL entries in an
     ImmutableList. (cnauroth)
 
+    HDFS-6028. Print clearer error message when user attempts to delete required
+    mask entry from ACL. (cnauroth)
+
 Release 2.3.1 - UNRELEASED
 
   INCOMPATIBLE CHANGES

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/AclTransformation.java

@@ -365,7 +365,7 @@ final class AclTransformation {
           maskDirty.contains(scope)) {
         // Caller explicitly removed mask entry, but it's required.
         throw new AclException(
-          "Invalid ACL: mask is required, but it was deleted.");
+          "Invalid ACL: mask is required and cannot be deleted.");
       } else if (providedMask.containsKey(scope) &&
           (!scopeDirty.contains(scope) || maskDirty.contains(scope))) {
         // Caller explicitly provided new mask, or we are preserving the existing