A way for showing pre-formatted output (e.g. tracebacks)

[rocky]

Right now we don't have a way to show pre-formatted output. And in tracebacks endings are wrapped:

System::exception:
Exception raised:  Traceback (most recent call last):  File "/src/external-vcs/github/Mathics3/mathics-django/mathics_django/web/views.py", line 265, in query result = evaluation.evaluate(expr, timeout=settings.TIMEOUT)  File "/src/external-vcs/github/mathics/Mathics/mathics/core/evaluation.py", line 361, in evaluate result = run_with_timeout_and_stack(evaluate, timeout, self)  File "/src/external-vcs/github/mathics/Mathics/mathics/core/evaluation.py", line 118, in run_with_timeout_and_stack return request()  File "/src/external-vcs/github/mathics/Mathics/mathics/core/evaluation.py", line 354, in evaluate return self.format_output(self.last_eval, format)  File "/src/external-vcs/github/Mathics3/mathics-django/mathics_django/web/models.py", line 33, in <lambda> evaluation, expr, format  File "/src/external-vcs/github/Mathics3/mathics-django/mathics_django/web/format.py", line 102, in format_output return eval_boxes(result, result.boxes_to_js, obj)  File "/src/external-vcs/github/Mathics3/mathics-django/mathics_django/web/format.py", line 32, in eval_boxes boxes = fn(evaluation=obj, **options)  File "/src/external-vcs/github/mathics/Mathics/mathics/builtin/box/graphics3d.py", line 339, in boxes_to_js j...

https://github.com/Mathics3/mathics-django/blob/master/mathics_django/web/views.py#L277-L282 is where we detect an error.