get_exception_info: fix get_exception_info for source=None (#233)
get_exception_info: fix get_exception_info for source=None (#233)

This might happen when a template with a base gets rendered, having the
error in the included template.

> {% extends "layout.html" %}

> {{ foo "bar" }}

> Error: ("expected token 'end of print statement', got 'string'",)

In the Jinja2 API it seems to be usual that `source` / `source_hint` can
be `None`.
niwinz/django-jinja,niwinz/django-jinja,akx/django-jinja,niwinz/django-jinja,akx/django-jinja,akx/django-jinja,akx/django-jinja