Rewrite coverage paths

Since tox is running tests on the installed package, the coverage paths are no
more relative to the repository root.

proteus/tox.ini

@@ -2,13 +2,13 @@
 envlist = py310,py311,py312,py313,py314
 
 [testenv]
-changedir = {toxworkdir}
+changedir = {env_site_packages_dir}
 extras = test
 commands =
-    coverage run --source=proteus --omit=*/tests/* -m xmlrunner discover -s proteus.tests {posargs}
+    coverage run --rcfile={toxinidir}/tox.ini --source=proteus --omit=*/tests/* -m xmlrunner discover -s proteus.tests {posargs}
 commands_post =
-    coverage report
-    coverage xml
+    coverage report --rcfile={toxinidir}/tox.ini
+    coverage xml --rcfile={toxinidir}/tox.ini -o {package_root}/coverage.xml
 deps =
     coverage
     unittest-xml-reporting
@@ -16,3 +16,6 @@ passenv = *
 setenv =
     TRYTOND_DATABASE_URI={env:TRYTOND_DATBASE_URI:sqlite://}
     DB_NAME={env:DB_NAME::memory:}
+
+[coverage:run]
+relative_files = true