Merge pull request #100 from bird-house/update_pytest_nbval

require pytest 6.0 and nbval 0.9.6

The newest major release of pytest (6.0.0) is now compatible with nbval at and above 0.9.6. No more need for specific pinned versions.

Author: Zeitsperre

{{cookiecutter.project_repo_name}}/requirements_dev.txt

@@ -1,11 +1,10 @@
-# https://github.com/computationalmodelling/nbval/issues/139 broken by pytest 6.0.0
-pytest==5.4.3
+pytest>=6.0
 flake8
 pytest-flake8
 ipython
 pytest-notebook
 nbsphinx
-nbval
+nbval>=0.9.6
 nbconvert
 sphinx>=1.7
 bumpversion