Use custom message when a non-zero Precondition Group fails.

src/Discord.Net.Commands/Attributes/PreconditionAttribute.cs

@@ -7,12 +7,9 @@ namespace Discord.Commands
     public abstract class PreconditionAttribute : Attribute
     {
         /// <summary>
-        /// Specify a group that this precondition belongs to.
-        /// Preconditions of the same group require only one
-        /// of the preconditions to pass in order to be
-        /// successful (A || B). Specifying <see cref="Group"/> = 0
-        /// or not at all will require *all* preconditions
-        /// to pass, just like normal (A && B).
+        /// Specify a group that this precondition belongs to. Preconditions of the same group require only one
+        /// of the preconditions to pass in order to be successful (A || B). Specifying <see cref="Group"/> = 0
+        /// or not at all will require *all* preconditions to pass, just like normal (A && B).
         /// </summary>
         public int Group { get; set; } = 0;
 

src/Discord.Net.Commands/Info/CommandInfo.cs

@@ -86,7 +86,7 @@ namespace Discord.Commands
                         results.Add(await precondition.CheckPermissions(context, this, services).ConfigureAwait(false));
 
                     if (!results.Any(p => p.IsSuccess))
-                        return results[0];
+                        return PreconditionResult.FromError($"Module precondition group {preconditionGroup.Key} failed: {String.Join("\n", results.Select(r => r.ErrorReason))}.");
                 }
             }
 
@@ -108,7 +108,7 @@ namespace Discord.Commands
                         results.Add(await precondition.CheckPermissions(context, this, services).ConfigureAwait(false));
 
                     if (!results.Any(p => p.IsSuccess))
-                        return results[0];
+                        return PreconditionResult.FromError($"Command precondition group {preconditionGroup.Key} failed: {String.Join("\n", results.Select(r => r.ErrorReason))}.");
                 }
             }