Pin cryptography version (#974)

* bump CI

* pin

* pin more

* no cache

* try again

* pypy3

* try this?

* Only install for pypy

* lower bound

* move to [tox]

* edit Makefile

* Revert unnecessary changes

Makefile

@@ -7,7 +7,7 @@ venv: $(VENV_NAME)/bin/activate
 $(VENV_NAME)/bin/activate: setup.py
 	$(PIP) install --upgrade pip virtualenv
 	@test -d $(VENV_NAME) || $(PYTHON) -m virtualenv --clear $(VENV_NAME)
-	${VENV_NAME}/bin/python -m pip install -U pip tox twine
+	${VENV_NAME}/bin/python -m pip install -U pip tox twine "cryptography<40"
 	${VENV_NAME}/bin/python -m pip install -e .
 	@touch $(VENV_NAME)/bin/activate