upgrade  pytest+pytest-django to eliminate dependencies on six (#7672)
upgrade  pytest+pytest-django to eliminate dependencies on six (#7672)

* upgrade to latest version of pytest+pytest-django to eliminate dependency on six

* rollback pytest to 6.1 as py35 is dropped in 6.2

Co-authored-by: Tom Christie <96835dd8bfa718bd6447ccc87af89ae1675daeca@tomchristie.com>
tomchristie/django-rest-framework,tomchristie/django-rest-framework,tomchristie/django-rest-framework