- Fix redirection in test where a file `nul` was created in working directory.
- Improve test by using functions instead of copying the code.
- Add option to configure message format via environment variables
`LOGGING_PIPELINE_WARNING_MESSAGE_FORMAT` and `LOGGING_PIPELINE_ERROR_MESSAGE_FORMAT`.
The value is used to configure the python logger with `{}`-format, see
[LogRecord attributes](https://docs.python.org/3/library/logging.html#logrecord-attributes).