CLI: log to stderr instead of stdout

Since the `ls` command produces machine-readable output, we need to ensure
that any log messages produced do not corrupt that output.

Logging to stderr is also conventional; Python's `StreamHandler` even
defaults to it.

This breaks the `import` command tests, because previously they were looking
at the last log message. I don't think we should be testing log messages, so
add a proper `print` to this command. This also makes it consistent with the
`create` command.

changelog.d/20241206_135902_roman_cli_logging.md

@@ -0,0 +1,4 @@
+### Changed
+
+- \[CLI\] Log messages are now printed on stderr rather than stdout
+  (<https://github.com/cvat-ai/cvat/pull/8784>)

cvat-cli/src/cvat_cli/_internal/commands.py

@@ -418,11 +418,12 @@ def configure_parser(self, parser: argparse.ArgumentParser) -> None:
         )
 
     def execute(self, client: Client, *, filename: str, status_check_period: int) -> None:
-        client.tasks.create_from_backup(
+        task = client.tasks.create_from_backup(
             filename=filename,
             status_check_period=status_check_period,
             pbar=DeferredTqdmProgressReporter(),
         )
+        print(f"Created task ID", task.id)
 
 
 @COMMANDS.command_class("auto-annotate")

cvat-cli/src/cvat_cli/_internal/common.py

@@ -74,7 +74,7 @@ def configure_logger(logger: logging.Logger, parsed_args: argparse.Namespace) ->
     formatter = logging.Formatter(
         "[%(asctime)s] %(levelname)s: %(message)s", datefmt="%Y-%m-%d %H:%M:%S", style="%"
     )
-    handler = logging.StreamHandler(sys.stdout)
+    handler = logging.StreamHandler(sys.stderr)
     handler.setFormatter(formatter)
     logger.addHandler(handler)
     logger.setLevel(level)