Pass child process log msgs to parent logger

Without that it's not possible to use caplog or other log capturing
mechanisms in unit tests.

QueueHandler in Child Process:
- The child process uses a QueueHandler to send log messages to the logger
  queue.

QueueListener in Parent Process:
- The parent process uses a QueueListener to listen for log messages from the
  child process and handle them using the parent logger's handlers.

Exception Handling:
- Exceptions raised in the child process are sent back to the parent process
  via the result queue.
- This helps with situations where failing functions executed in a child
  process lead to the last traceback point to be something like:
  ```
  File "/usr/lib/python2.7/site-packages/convert2rhel/utils.py", line 246, in wrapper
    raise process.exception
  ```

Assisted by GitHub Copilot.

Author: bocekm

convert2rhel/pkghandler.py

@@ -299,7 +299,7 @@ def get_files_owned_by_package(installed_pkg_name):
     if ret_code != 0:
         logger.warning("Failed to list files for package {0}: {1}".format(installed_pkg_name, output))
         return []
-    return output.decode("utf-8").splitlines()
+    return output.splitlines()
 
 
 @utils.run_as_child_process

convert2rhel/unit_tests/pkghandler_test.py

@@ -1860,3 +1860,35 @@ def test_get_highest_package_version(packages, expected):
 def test_get_highest_package_version_value_err(packages):
     with pytest.raises(ValueError):
         pkghandler.get_highest_package_version(pkgs=packages)
+
+
+@pytest.mark.parametrize(
+    "installed_pkg_name, subprocess_output, subprocess_ret_code, expected_files, expected_warning",
+    [
+        ("pkg1", "/etc/file1\n/etc/file2\n", 0, ["/etc/file1", "/etc/file2"], None),
+        ("pkg2", "", 0, [], None),
+        (
+            "pkg3",
+            "package pkg3 is not installed\n",
+            1,
+            [],
+            "Failed to list files for package pkg3: package pkg3 is not installed",
+        ),
+    ],
+)
+def test_get_files_owned_by_package(
+    monkeypatch, caplog, installed_pkg_name, subprocess_output, subprocess_ret_code, expected_files, expected_warning
+):
+    def mock_run_subprocess(cmd, print_cmd=False, print_output=False):
+        return subprocess_output, subprocess_ret_code
+
+    monkeypatch.setattr(utils, "run_subprocess", mock_run_subprocess)
+
+    result = pkghandler.get_files_owned_by_package(installed_pkg_name)
+
+    assert result == expected_files
+
+    if expected_warning:
+        assert expected_warning in caplog.text
+    else:
+        assert "Failed to list files" not in caplog.text

convert2rhel/utils/__init__.py

@@ -20,6 +20,7 @@
 import fcntl
 import getpass
 import json
+import logging
 import multiprocessing
 import os
 import re
@@ -224,11 +225,25 @@ def inner_wrapper(*args, **kwargs):
             """
             func = kwargs.pop("func")
             queue = kwargs.pop("queue")
-            result = func(*args, **kwargs)
-            queue.put(result)
+            logger_queue = kwargs.pop("logger_queue")
+
+            # Redirect log messages to the logger queue
+            queue_handler = logging.handlers.QueueHandler(logger_queue)
+            logger = logging.getLogger()
+            logger.addHandler(queue_handler)
+
+            try:
+                result = func(*args, **kwargs)
+                queue.put(result)
+            except Exception as e:
+                queue.put(e)
+            finally:
+                logger.removeHandler(queue_handler)
 
         queue = multiprocessing.Queue()
-        kwargs.update({"func": func, "queue": queue})
+        logger_queue = multiprocessing.Queue()
+        kwargs.update({"func": func, "queue": queue, "logger_queue": logger_queue})
+
         process = Process(target=inner_wrapper, args=args, kwargs=kwargs)
 
         # Running the process as a daemon prevents it from hanging if a SIGINT
@@ -237,7 +252,12 @@ def inner_wrapper(*args, **kwargs):
         process.daemon = True
         try:
             process.start()
+            # Set up a listener for log messages from the child process
+            listener = logging.handlers.QueueListener(logger_queue, *logging.getLogger().handlers)
+            listener.start()
+
             process.join()
+            listener.stop()
 
             if process.exception:
                 raise process.exception