Catch Wikidata API errors and retry

Retry API error calls with exponential backoff.

Send mail to admin if errors continue after retries.

Includes a test.

tests/test_wikidata_api.py

@@ -0,0 +1,33 @@
+import pytest
+import pytest_mock
+import responses
+from geocode.wikidata import APIResponseError, api_call
+
+
+@responses.activate
+def test_api_call_retries_on_failure(mocker: pytest_mock.plugin.MockerFixture) -> None:
+    """Test retry for API calls."""
+    # Patch 'time.sleep' to instantly return, effectively skipping the sleep
+    mocked_sleep = mocker.patch("time.sleep", return_value=None)
+
+    mock_send_mail = mocker.patch("geocode.mail.send_to_admin")
+
+    responses.add(
+        responses.GET,
+        "https://www.wikidata.org/w/api.php",
+        body="bad request",
+        status=400,
+    )
+    with pytest.raises(APIResponseError):
+        api_call({"action": "wbgetentities", "ids": "Q42"})
+    assert len(responses.calls) == 5  # Assuming max_tries is 5
+
+    assert mocked_sleep.call_count == 4
+
+    mock_send_mail.assert_called()
+
+    send_mail_call = mock_send_mail.call_args_list[0]
+    assert send_mail_call[0] == (
+        "Geocode error",
+        "Error making Wikidata API call\n\nbad request",
+    )