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

--- pipdeptree-2.23.4/tox.ini.orig
+++ pipdeptree-2.23.4/tox.ini
@@ -33,7 +33,6 @@
       --cov-report html:{env_tmp_dir}{/}htmlcov --cov-report xml:{work_dir}{/}coverage.{env_name}.xml \
       --junitxml {work_dir}{/}junit.{env_name}.xml \
       tests}
-    diff-cover --compare-branch {env:DIFF_AGAINST:origin/main} {work_dir}{/}coverage.{env_name}.xml --fail-under 100
 
 [testenv:fix]
 description = format the code base to adhere to our styles, and complain about what we cannot do automatically
--- pipdeptree-2.23.4/pyproject.toml.orig
+++ pipdeptree-2.23.4/pyproject.toml
@@ -49,7 +49,6 @@
 ]
 optional-dependencies.test = [
   "covdefaults>=2.3",
-  "diff-cover>=9.1.1",
   "pytest>=8.3.2",
   "pytest-console-scripts>=1.4.1",
   "pytest-cov>=5",