Split up logging configuration method

#3

The `configure_logging()` method did multiple things: find and import a
logging configuration module, load the logging configuration dictionary,
and apply the dictionary configuration to the Python logger.

This commit will refactor `configure_logging()` into two methods.

1. `find_and_load_logging_conf()` will return a dictionary configuration
2. `configure_logging()` will apply the dictionary configuration

The return value of `configure_logging()` will remain the same, so there
will not be any changes to the programming API.

Also, now that the `configure_logging()` method is in the same module as
the logging configuration dictionary, that dictionary will be used by
default, instead of finding the module separately.

inboard/logging_conf.py

@@ -4,30 +4,42 @@
 import os
 import sys
 from pathlib import Path
+from typing import Optional
+
+
+def find_and_load_logging_conf(logging_conf: str) -> dict:
+    """Find and load a logging configuration module or file."""
+    logging_conf_path = Path(logging_conf)
+    spec = (
+        importlib.util.spec_from_file_location("confspec", logging_conf_path)
+        if logging_conf_path.is_file() and logging_conf_path.suffix == ".py"
+        else importlib.util.find_spec(logging_conf)
+    )
+    if not spec:
+        raise ImportError(f"Unable to import {logging_conf_path}")
+    logging_conf_module = importlib.util.module_from_spec(spec)
+    exec_module = getattr(spec.loader, "exec_module")
+    exec_module(logging_conf_module)
+    if not hasattr(logging_conf_module, "LOGGING_CONFIG"):
+        raise AttributeError(f"No LOGGING_CONFIG in {logging_conf_module.__name__}")
+    logging_conf_dict = getattr(logging_conf_module, "LOGGING_CONFIG")
+    if not isinstance(logging_conf_dict, dict):
+        raise TypeError("LOGGING_CONFIG is not a dictionary instance")
+    return logging_conf_dict
 
 
 def configure_logging(
     logger: logging.Logger = logging.getLogger(),
-    logging_conf: str = os.getenv("LOGGING_CONF", "inboard.logging_conf"),
+    logging_conf: Optional[str] = os.getenv("LOGGING_CONF"),
 ) -> dict:
-    """Configure Python logging based on a path to a logging module or file."""
+    """Configure Python logging given the name of a logging module or file."""
     try:
-        logging_conf_path = Path(logging_conf)
-        spec = (
-            importlib.util.spec_from_file_location("confspec", logging_conf_path)
-            if logging_conf_path.is_file() and logging_conf_path.suffix == ".py"
-            else importlib.util.find_spec(logging_conf)
-        )
-        if not spec:
-            raise ImportError(f"Unable to import {logging_conf}")
-        logging_conf_module = importlib.util.module_from_spec(spec)
-        exec_module = getattr(spec.loader, "exec_module")
-        exec_module(logging_conf_module)
-        if not hasattr(logging_conf_module, "LOGGING_CONFIG"):
-            raise AttributeError(f"No LOGGING_CONFIG in {logging_conf_module.__name__}")
-        logging_conf_dict = getattr(logging_conf_module, "LOGGING_CONFIG")
-        if not isinstance(logging_conf_dict, dict):
-            raise TypeError("LOGGING_CONFIG is not a dictionary instance")
+        if not logging_conf:
+            logging_conf_path = __name__
+            logging_conf_dict = LOGGING_CONFIG
+        else:
+            logging_conf_path = logging_conf
+            logging_conf_dict = find_and_load_logging_conf(logging_conf_path)
         logging.config.dictConfig(logging_conf_dict)
         logger.debug(f"Logging dict config loaded from {logging_conf_path}.")
         return logging_conf_dict