Fixed problem with env config vars.

nomad/config.py

@@ -342,7 +342,13 @@ def _apply(key, value, raise_error: bool = True) -> None:
     leading to ``config.fs.staging``.
     '''
     full_key = key
-    group_key, config_key = full_key.split('_', 1)
+    try:
+        group_key, config_key = full_key.split('_', 1)
+    except Exception:
+        if raise_error:
+            logger.error(f'config key does not exist: {full_key}')
+        return
+
     current = globals()
 
     if group_key not in current:

tests/test_config.py

@@ -51,6 +51,9 @@ def test_apply(with_config, caplog):
     config._apply('max_entry_download', 'not_a_number')
     assert_log(caplog, 'ERROR', 'cannot set')
 
+    config._apply('nounderscore', 'test_value')
+    assert_log(caplog, 'ERROR', 'nounderscore does not exist')
+
 
 def test_env(with_config, monkeypatch):
     monkeypatch.setattr('os.environ', dict(NOMAD_FS_PUBLIC='test_value'))