diff --git a/swh/indexer/storage/api/server.py b/swh/indexer/storage/api/server.py
--- a/swh/indexer/storage/api/server.py
+++ b/swh/indexer/storage/api/server.py
@@ -1,10 +1,11 @@
-# Copyright (C) 2015-2019  The Software Heritage developers
+# Copyright (C) 2015-2020  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 logging
 import os
+from typing import Any, Dict, Optional
 
 from swh.core import config
 from swh.core.api import RPCServerApp
@@ -54,14 +55,16 @@
 api_cfg = None
 
 
-def load_and_check_config(config_file, type="local"):
+def load_and_check_config(
+    config_path: Optional[str], type: str = "local"
+) -> Dict[str, Any]:
     """Check the minimal configuration is set to run the api or raise an
        error explanation.
 
     Args:
-        config_file (str): Path to the configuration file to load
-        type (str): configuration type. For 'local' type, more
-                    checks are done.
+        config_path: Path to the configuration file to load
+        type: configuration type. For 'local' type, more
+          checks are done.
 
     Raises:
         Error if the setup is not as expected
@@ -70,13 +73,13 @@
         configuration as a dict
 
     """
-    if not config_file:
+    if not config_path:
         raise EnvironmentError("Configuration file must be defined")
 
-    if not os.path.exists(config_file):
-        raise FileNotFoundError("Configuration file %s does not exist" % (config_file,))
+    if not os.path.exists(config_path):
+        raise FileNotFoundError(f"Configuration file {config_path} does not exist")
 
-    cfg = config.read(config_file)
+    cfg = config.read(config_path)
     if "indexer_storage" not in cfg:
         raise KeyError("Missing '%indexer_storage' configuration")
 
@@ -106,8 +109,8 @@
     """
     global api_cfg
     if not api_cfg:
-        config_file = os.environ.get("SWH_CONFIG_FILENAME")
-        api_cfg = load_and_check_config(config_file)
+        config_path = os.environ.get("SWH_CONFIG_FILENAME")
+        api_cfg = load_and_check_config(config_path)
         app.config.update(api_cfg)
     handler = logging.StreamHandler()
     app.logger.addHandler(handler)
diff --git a/swh/indexer/tests/storage/test_server.py b/swh/indexer/tests/storage/test_server.py
--- a/swh/indexer/tests/storage/test_server.py
+++ b/swh/indexer/tests/storage/test_server.py
@@ -31,53 +31,49 @@
     return str(config_path)
 
 
-def test_load_and_check_config_no_configuration() -> None:
+@pytest.mark.parametrize("config_path", [None, ""])
+def test_load_and_check_config_no_configuration(config_path) -> None:
     """Inexistent configuration files raises"""
-    with pytest.raises(EnvironmentError) as e:
-        load_and_check_config(None)
+    with pytest.raises(EnvironmentError, match="Configuration file must be defined"):
+        load_and_check_config(config_path)
 
-    assert e.value.args[0] == "Configuration file must be defined"
 
+def test_load_and_check_inexistent_config_path() -> None:
     config_path = "/indexer/inexistent/config.yml"
-    with pytest.raises(FileNotFoundError) as e:
+    expected_error = f"Configuration file {config_path} does not exist"
+    with pytest.raises(FileNotFoundError, match=expected_error):
         load_and_check_config(config_path)
 
-    assert e.value.args[0] == "Configuration file %s does not exist" % (config_path,)
-
 
 def test_load_and_check_config_wrong_configuration(tmpdir) -> None:
     """Wrong configuration raises"""
     config_path = prepare_config_file(tmpdir, "something: useless")
-    with pytest.raises(KeyError) as e:
+    with pytest.raises(KeyError, match="Missing '%indexer_storage' configuration"):
         load_and_check_config(config_path)
 
-    assert e.value.args[0] == "Missing '%indexer_storage' configuration"
-
 
 def test_load_and_check_config_remote_config_local_type_raise(tmpdir) -> None:
     """'local' configuration without 'local' storage raises"""
     config = {"indexer_storage": {"cls": "remote", "args": {}}}
     config_path = prepare_config_file(tmpdir, config)
-    with pytest.raises(ValueError) as e:
-        load_and_check_config(config_path, type="local")
 
-    assert (
-        e.value.args[0]
-        == "The indexer_storage backend can only be started with a 'local' "
+    expected_error = (
+        "The indexer_storage backend can only be started with a 'local' "
         "configuration"
     )
+    with pytest.raises(ValueError, match=expected_error):
+        load_and_check_config(config_path, type="local")
 
 
 def test_load_and_check_config_local_incomplete_configuration(tmpdir) -> None:
     """Incomplete 'local' configuration should raise"""
     config = {"indexer_storage": {"cls": "local", "args": {}}}
 
+    expected_error = "Invalid configuration; missing 'db' config entry"
     config_path = prepare_config_file(tmpdir, config)
-    with pytest.raises(ValueError) as e:
+    with pytest.raises(ValueError, match=expected_error):
         load_and_check_config(config_path)
 
-    assert e.value.args[0] == "Invalid configuration; missing 'db' config entry"
-
 
 def test_load_and_check_config_local_config_fine(tmpdir) -> None:
     """'Remote configuration is fine"""