Better error message for task.scope (#54180)

Fixes #54178

Author: LilithHafner

base/task.jl

@@ -179,7 +179,9 @@ end
         # TODO: this field name should be deprecated in 2.0
         return t._isexception ? t.result : nothing
     elseif field === :scope
-        error("Querying `scope` is disallowed. Use `current_scope` instead.")
+        error("""
+            Querying a Task's `scope` field is disallowed.
+            The private `Core.current_scope()` function is better, though still an implementation detail.""")
     else
         return getfield(t, field)
     end

test/channels.jl

@@ -642,6 +642,7 @@ end
 @testset "Task properties" begin
     f() = rand(2,2)
     t = Task(f)
-    @test_throws ErrorException("Querying `scope` is disallowed. Use `current_scope` instead.") t.scope
+    message = "Querying a Task's `scope` field is disallowed.\nThe private `Core.current_scope()` function is better, though still an implementation detail."
+    @test_throws ErrorException(message) t.scope
     @test t.state == :runnable
 end