allow for missing cffi on 3.13

Author: davidhewitt

examples/rust_with_cffi/noxfile.py

@@ -7,7 +7,13 @@
 
 @nox.session()
 def test(session: nox.Session):
-    session.install(SETUPTOOLS_RUST, "wheel", "pytest", "cffi")
+    session.install(SETUPTOOLS_RUST, "wheel", "pytest")
+
+    try:
+        session.install("cffi", "--only-binary=cffi")
+    except nox.command.CommandFailed:
+        session.skip("cffi not available on this platform")
+
     # Ensure build uses version of setuptools-rust under development
     session.install("--no-build-isolation", ".")
     # Test Python package