Tests: Add rerun functionality for tests

We add pytest-rerun to tests and allow the tests to be rerun up to 3
times until they pass. The tests for lab 4 are less stable and fail at
different points for different reasons that are hard to fix. By allowing
the tests to pass with a rerun we avoid these kind of issues.

tox.ini

@@ -24,6 +24,7 @@ setenv =
     JUPYTER_DATA_DIR={envdir}/share/jupyter
 deps =
     pytest<8.0.0
+    pytest-rerunfailures
     pytest-html<4.0.0,
     # selenium juypter notebook tests
     jupyterlab==3.6.5
@@ -41,7 +42,7 @@ deps =
 commands =
     # converts the python files to ipython notebooks
     jupytext tests/notebooks/*.py --to ipynb
-    pytest {posargs:-v} --driver Firefox
+    pytest {posargs:-v} --reruns 2 --driver Firefox
 
 [testenv:tests-lab-4]
 description =
@@ -56,6 +57,7 @@ setenv =
     JUPYTER_DATA_DIR={envdir}/share/jupyter
 deps =
     pytest<8.0.0
+    pytest-rerunfailures
     pytest-html<4.0.0,
     # selenium juypter notebook tests
     jupyterlab>=4.0.0
@@ -73,7 +75,7 @@ deps =
 commands =
     # converts the python files to ipython notebooks
     jupytext tests/notebooks/*.py --to ipynb
-    pytest {posargs:-v} -m "not matplotlib" --driver Firefox
+    pytest {posargs:-v} -m "not matplotlib" --reruns 2 --driver Firefox
 
 [testenv:coverage]
 # We do coverage in a separate environment that skips the selenium tests but