The files in the data_files list are already installed by the deb
package, so they need not to be installed by the Python package.
Index: afancontrol/setup.py
===================================================================
--- afancontrol.orig/setup.py
+++ afancontrol/setup.py
@@ -9,8 +9,4 @@ with open("src/afancontrol/__init__.py",
 
 setup(
     version=version,
-    data_files=[
-        ("etc/afancontrol", ["pkg/afancontrol.conf"]),
-        ("etc/systemd/system", ["pkg/afancontrol.service"]),
-    ],
 )