test: add skips to accommodate a DBpedia outage

DBpedia is failing right now. This change adds narrow skips to the tests
that use it which only trigger for connection related problems, so the
test suite can pass even when DBpedia is down.

Test that use external services should be avoided if possible and should
be replaced with the HTTP mocking facilities of the test framework.

test/test_examples.py

@@ -1,3 +1,4 @@
+import logging
 import subprocess
 import sys
 from pathlib import Path
@@ -29,4 +30,21 @@ def test_example(example_file: Path) -> None:
         # this example requires a berkeleydb installation
         pytest.skip("The BerkeleyDB example is not working correctly.")
 
-    subprocess.run([sys.executable, f"{example_file}"], check=True)
+    result = subprocess.run(
+        [sys.executable, f"{example_file}"],
+        stdout=subprocess.PIPE,
+        stderr=subprocess.PIPE,
+    )
+
+    logging.debug("result = %s", result)
+
+    try:
+        result.check_returncode()
+    except subprocess.CalledProcessError:
+        if (
+            example_file.stem == "sparqlstore_example"
+            and "http.client.RemoteDisconnected: Remote end closed connection without response"
+            in result.stderr.decode("utf-8")
+        ):
+            pytest.skip("this test uses dbpedia which is down sometimes")
+        raise

test/test_sparql/test_service.py

@@ -1,4 +1,5 @@
 import json
+from http.client import RemoteDisconnected
 from test.utils import helper
 from test.utils.http import MethodName, MockHTTPResponse
 from test.utils.httpservermock import ServedBaseHTTPServerMock
@@ -181,7 +182,10 @@ def test_service_with_implicit_select_and_allcaps():
         ?s <http://www.w3.org/2002/07/owl#sameAs> ?sameAs .
       }
     } LIMIT 3"""
-    results = helper.query_with_retry(g, q)
+    try:
+        results = helper.query_with_retry(g, q)
+    except RemoteDisconnected:
+        pytest.skip("this test uses dbpedia which is down sometimes")
     assert len(results) == 3