We cannot compare against origin/main branch because we build from sdist, not git.

--- filelock-3.16.1/tox.ini.orig
+++ filelock-3.16.1/tox.ini
@@ -32,7 +32,7 @@
       --cov-config=pyproject.toml --no-cov-on-fail --cov-report term-missing:skip-covered --cov-context=test \
       --cov-report html:{envtmpdir}{/}htmlcov --cov-report xml:{toxworkdir}{/}coverage.{envname}.xml \
       tests
-    diff-cover --compare-branch {env:DIFF_AGAINST:origin/main} {toxworkdir}{/}coverage.{envname}.xml}
+    }
 
 [testenv:fix]
 description = format the code base to adhere to our styles, and complain about what we cannot do automatically
--- filelock-3.16.1/pyproject.toml.orig
+++ filelock-3.16.1/pyproject.toml
@@ -49,7 +49,6 @@
 optional-dependencies.testing = [
   "covdefaults>=2.3",
   "coverage>=7.6.1",
-  "diff-cover>=9.2",
   "pytest>=8.3.3",
   "pytest-asyncio>=0.24",
   "pytest-cov>=5",