try this

Author: gizmoguy

debian/patches/0002-Avoid-setuptools-PackageDiscoveryError.patch

@@ -2,11 +2,14 @@ Index: python3-prometheus-client/pyproject.toml
 ===================================================================
 --- python3-prometheus-client.orig/pyproject.toml
 +++ python3-prometheus-client/pyproject.toml
-@@ -47,3 +47,7 @@ Documentation = "https://prometheus.gith
+@@ -47,3 +47,10 @@ Documentation = "https://prometheus.gith
 
  [tool.setuptools.package-data]
  prometheus_client = ['py.typed']
 +
++[tool.setuptools.data-files]
++"tests" = ["tests/certs/*"]
++
 +[tool.setuptools.packages.find]
 +where = ["."]
 +exclude = ["debian"]