Complete the refactor and test improvements

src/dotnet/CommandLine/CommandParsingException.cs

@@ -2,11 +2,14 @@
 // Licensed under the MIT license. See LICENSE file in the project root for full license information.
 
 using System;
+using Microsoft.DotNet.Tools;
 
 namespace Microsoft.DotNet.Cli.CommandLine
 {
     internal class CommandParsingException : Exception
     {
+        private bool _isRequireSubCommandMissing;
+
         public CommandParsingException(
             CommandLineApplication command,
             string message,
@@ -14,10 +17,19 @@ namespace Microsoft.DotNet.Cli.CommandLine
             : base(message)
         {
             Command = command;
-            IsRequireSubCommandMissing = isRequireSubCommandMissing;
+            _isRequireSubCommandMissing = isRequireSubCommandMissing;
         }
 
         public CommandLineApplication Command { get; }
-        public bool IsRequireSubCommandMissing { get; }
+
+        public override string Message
+        {
+            get
+            {
+                return _isRequireSubCommandMissing
+                     ? CommonLocalizableStrings.RequiredCommandNotPassed
+                     : base.Message;
+            }
+        }
     }
 }