diff --git a/swh/search/tests/test_cli.py b/swh/search/tests/test_cli.py
index 9133e0b..6d3419e 100644
--- a/swh/search/tests/test_cli.py
+++ b/swh/search/tests/test_cli.py
@@ -1,175 +1,175 @@
 # Copyright (C) 2019-2020  The Software Heritage developers
 # See the AUTHORS file at the top-level directory of this distribution
 # License: GNU General Public License version 3, or any later version
 # See top-level LICENSE file for more information
 
 import copy
 import tempfile
 import yaml
 
 import pytest
 
 from confluent_kafka import Producer
 from click.testing import CliRunner
 
 from swh.journal.serializers import value_to_kafka
 
 from swh.search.cli import cli
 
 
 CLI_CONFIG = """
 search:
     cls: elasticsearch
     args:
         hosts:
-        - '{elasticsearch_host}'
+        - '%(elasticsearch_host)s'
 """
 
 JOURNAL_OBJECTS_CONFIG_TEMPLATE = """
 journal:
     brokers:
         - {broker}
     prefix: {prefix}
     group_id: {group_id}
 """
 
 
 def invoke(catch_exceptions, args, config="", *, elasticsearch_host):
     runner = CliRunner()
     with tempfile.NamedTemporaryFile("a", suffix=".yml") as config_fd:
         config_fd.write(
-            (CLI_CONFIG + config).format(elasticsearch_host=elasticsearch_host)
+            (CLI_CONFIG + config) % {"elasticsearch_host": elasticsearch_host}
         )
         config_fd.seek(0)
         result = runner.invoke(cli, ["-C" + config_fd.name] + args)
     if not catch_exceptions and result.exception:
         print(result.output)
         raise result.exception
     return result
 
 
 def test__journal_client__origin(
     swh_search, elasticsearch_host: str, kafka_prefix: str, kafka_server
 ):
     """Tests the re-indexing when origin_batch_size*task_batch_size is a
     divisor of nb_origins."""
     producer = Producer(
         {
             "bootstrap.servers": kafka_server,
             "client.id": "test search origin producer",
             "acks": "all",
         }
     )
     origin_foobar_baz = {
         "url": "http://foobar.baz",
     }
     value = value_to_kafka(origin_foobar_baz)
     topic = f"{kafka_prefix}.origin"
     producer.produce(topic=topic, key=b"bogus-origin", value=value)
 
     journal_objects_config = JOURNAL_OBJECTS_CONFIG_TEMPLATE.format(
         broker=kafka_server, prefix=kafka_prefix, group_id="test-consumer"
     )
     result = invoke(
         False,
         ["journal-client", "objects", "--stop-after-objects", "1",],
         journal_objects_config,
         elasticsearch_host=elasticsearch_host,
     )
 
     # Check the output
     expected_output = "Processed 1 messages.\nDone.\n"
     assert result.exit_code == 0, result.output
     assert result.output == expected_output
 
     swh_search.flush()
 
     # searching origin without visit as requirement
     actual_page = swh_search.origin_search(url_pattern="foobar")
     # We find it
     assert actual_page.next_page_token is None
     assert actual_page.results == [origin_foobar_baz]
 
     # It's an origin with no visit, searching for it with visit
     actual_page = swh_search.origin_search(url_pattern="foobar", with_visit=True)
     # returns nothing
     assert actual_page.next_page_token is None
     assert actual_page.results == []
 
 
 def test__journal_client__origin_visit(
     swh_search, elasticsearch_host, kafka_prefix: str, kafka_server
 ):
     """Tests the re-indexing when origin_batch_size*task_batch_size is a
     divisor of nb_origins."""
     origin_foobar = {"url": "http://baz.foobar"}
     producer = Producer(
         {
             "bootstrap.servers": kafka_server,
             "client.id": "test search origin visit producer",
             "acks": "all",
         }
     )
     topic = f"{kafka_prefix}.origin_visit"
     value = value_to_kafka({"origin": origin_foobar["url"]})
     producer.produce(topic=topic, key=b"bogus-origin-visit", value=value)
 
     journal_objects_config = JOURNAL_OBJECTS_CONFIG_TEMPLATE.format(
         broker=kafka_server, prefix=kafka_prefix, group_id="test-consumer"
     )
     result = invoke(
         False,
         ["journal-client", "objects", "--stop-after-objects", "1",],
         journal_objects_config,
         elasticsearch_host=elasticsearch_host,
     )
 
     # Check the output
     expected_output = "Processed 1 messages.\nDone.\n"
     assert result.exit_code == 0, result.output
     assert result.output == expected_output
 
     swh_search.flush()
 
     # Both search returns the visit
     actual_page = swh_search.origin_search(url_pattern="foobar", with_visit=False)
     assert actual_page.next_page_token is None
     assert actual_page.results == [origin_foobar]
 
     actual_page = swh_search.origin_search(url_pattern="foobar", with_visit=True)
     assert actual_page.next_page_token is None
     assert actual_page.results == [origin_foobar]
 
 
 def test__journal_client__missing_main_journal_config_key(elasticsearch_host):
     """Missing configuration on journal should raise"""
     with pytest.raises(KeyError, match="journal"):
         invoke(
             catch_exceptions=False,
             args=["journal-client", "objects", "--stop-after-objects", "1",],
             config="",  # missing config will make it raise
             elasticsearch_host=elasticsearch_host,
         )
 
 
 def test__journal_client__missing_journal_config_keys(elasticsearch_host):
     """Missing configuration on mandatory journal keys should raise"""
     journal_objects_config = JOURNAL_OBJECTS_CONFIG_TEMPLATE.format(
         broker="192.0.2.1", prefix="swh.journal.objects", group_id="test-consumer"
     )
     journal_config = yaml.safe_load(journal_objects_config)
 
     for key in journal_config["journal"].keys():
         if key == "prefix":  # optional
             continue
         cfg = copy.deepcopy(journal_config)
         del cfg["journal"][key]  # make config incomplete
         yaml_cfg = yaml.dump(cfg)
 
         with pytest.raises(TypeError, match=f"{key}"):
             invoke(
                 catch_exceptions=False,
                 args=["journal-client", "objects", "--stop-after-objects", "1",],
                 config=yaml_cfg,  # incomplete config will make the cli raise
                 elasticsearch_host=elasticsearch_host,
             )