Merge pull request #1433 from pitachips/call_error_message

fix error message for __call__ for non-callable objects

vm/src/vm.rs

@@ -603,10 +603,13 @@ impl VirtualMachine {
             self.invoke(&function, args.insert(object.clone()))
         } else if let Some(PyBuiltinFunction { ref value }) = func_ref.payload() {
             value(self, args)
-        } else {
-            // TODO: is it safe to just invoke __call__ otherwise?
-            vm_trace!("invoke __call__ for: {:?}", &func_ref.payload);
+        } else if self.is_callable(&func_ref) {
             self.call_method(&func_ref, "__call__", args)
+        } else {
+            Err(self.new_type_error(format!(
+                "'{}' object is not callable",
+                func_ref.class().name
+            )))
         }
     }