We test in proto area not in site-packages.

--- filelock-3.20.0/tox.toml.orig
+++ filelock-3.20.0/tox.toml
@@ -19,7 +19,7 @@
     { replace = "posargs", extend = true, default = [
       "--no-cov-on-fail",
       "--cov",
-      "{env_site_packages_dir}{/}filelock",
+      "filelock",
       "--cov",
       "{tox_root}{/}tests",
       "--cov-config",