diff --git a/Python/Examples/tests/conftest.py b/Python/Examples/tests/conftest.py
index c5dfc83d959..ea61e7d3a36 100644
--- a/Python/Examples/tests/conftest.py
+++ b/Python/Examples/tests/conftest.py
@@ -52,11 +52,12 @@ def __init__(
 
 def _parse_hash_file(file: Path) -> Dict[str, str]:
     res = {}
-    for line in file.open():
-        if line.strip() == "" or line.strip().startswith("#"):
-            continue
-        key, h = line.strip().split(":", 1)
-        res[key.strip()] = h.strip()
+    with file.open() as f:
+        for line in f:
+            if line.strip() == "" or line.strip().startswith("#"):
+                continue
+            key, h = line.strip().split(":", 1)
+            res[key.strip()] = h.strip()
     return res
 
 
diff --git a/pytest.ini b/pytest.ini
index f3d519c36aa..00b5f835594 100644
--- a/pytest.ini
+++ b/pytest.ini
@@ -14,3 +14,5 @@ markers =
     edm4hep
     odd
     hepmc3
+filterwarnings =
+    error