Add test for temporary file is closed/deleted.
Add test for temporary file is closed/deleted.

incuna/django-wkhtmltopdf,incuna/django-wkhtmltopdf,halfnibble/django-wkhtmltopdf,tclancy/django-wkhtmltopdf,tclancy/django-wkhtmltopdf,halfnibble/django-wkhtmltopdf