Fix error message when adding a reviewer that does not exist

If the name given for a reviewer does not match to a user the
code falls into trying to match a group. If it also does not
match a group, report that neither is found instead of saying
"Group Not Found:user@example.com".

Change-Id: I09fd4448508430faa4fdd893687f7a0def2e1141

gerrit-server/src/main/java/com/google/gerrit/server/change/ChangeMessages.java

@@ -23,6 +23,7 @@ public class ChangeMessages extends TranslationBundle {
   }
 
   public String revertChangeDefaultMessage;
+  public String reviewerNotFound;
 
   public String groupIsNotAllowed;
   public String groupHasTooManyMembers;

gerrit-server/src/main/java/com/google/gerrit/server/change/PostReviewers.java

@@ -129,7 +129,13 @@ public class PostReviewers implements RestModifyView<ChangeResource, Input> {
       Account.Id accountId = accounts.parse(input.reviewer).getAccountId();
       return putAccount(reviewerFactory.create(rsrc, accountId));
     } catch (UnprocessableEntityException e) {
-      return putGroup(rsrc, input);
+      try {
+        return putGroup(rsrc, input);
+      } catch (UnprocessableEntityException e2) {
+        throw new UnprocessableEntityException(MessageFormat.format(
+            ChangeMessages.get().reviewerNotFound,
+            input.reviewer));
+      }
     }
   }
 

gerrit-server/src/main/resources/com/google/gerrit/server/change/ChangeMessages.properties

@@ -1,6 +1,7 @@
 # Changes to this file should also be made in
 # gerrit-gwtui/src/main/java/com/google/gerrit/client/changes/ChangeMessages.properties
 revertChangeDefaultMessage = Revert \"{0}\"\n\nThis reverts commit {1}
+reviewerNotFound = {0} does not identify a registered user or group
 
 groupIsNotAllowed =  The group {0} cannot be added as reviewer.
 groupHasTooManyMembers = The group {0} has too many members to add them all as reviewers.