drop safety (#295)

GitHub has dependency alerts and dependency security updates
that can replace `safety`.

For the past few months, safety has been raising vulnerability
errors for `pip` and now `jinja2`. The latter is a dependency
of `safety` itself, and both CVEs are disputed.

Which is breaking CI for us.

.github/workflows/tests.yml

@@ -45,8 +45,8 @@ jobs:
         pip --version
         nox --version
 
-    - name: Lint code and check dependencies
-      run: nox -s lint safety
+    - name: Lint code
+      run: nox -s lint
 
     - name: Run tests
       run: nox -s tests-${{ matrix.nox_pyv || matrix.pyv }} -- --cov-report=xml

noxfile.py

@@ -40,14 +40,6 @@ def lint(session: nox.Session) -> None:
     session.run("python", "-m", "mypy")
 
 
-@nox.session
-def safety(session: nox.Session) -> None:
-    """Scan dependencies for insecure packages."""
-    session.install(".[dev]", *pip_dev_flags)
-    session.install("safety")
-    session.run("safety", "check", "--full-report")
-
-
 @nox.session
 def build(session: nox.Session) -> None:
     session.install("build", "setuptools", "twine")