Error in logging: TypeError: not all arguments converted during string formatting

[sjagoe]

When running haas with --log-level=debug and discovering tests from a file path, an exception is raised from the logging module, caused by incorrect logging usage.

2019-03-27 12:24:33,665 DEBUG    [haas.plugins.discoverer:205] Starting test discovery
--- Logging error ---
Traceback (most recent call last):
  File "/Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/logging/__init__.py", line 1034, in emit
    msg = self.format(record)
  File "/Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/logging/__init__.py", line 880, in format
    return fmt.format(record)
  File "/Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/logging/__init__.py", line 619, in format
    record.message = record.getMessage()
  File "/Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/logging/__init__.py", line 380, in getMessage
    msg = msg % self.args
TypeError: not all arguments converted during string formatting
Call stack:
  File "/Users/sjagoe/.local/share/virtualenvs/locust/bin/haas", line 10, in <module>
    sys.exit(main())
  File "/Users/sjagoe/.local/share/virtualenvs/locust/lib/python3.7/site-packages/haas/main.py", line 24, in main
    return application.run()
  File "/Users/sjagoe/.local/share/virtualenvs/locust/lib/python3.7/site-packages/haas/haas_application.py", line 115, in run
    for start in args.start
  File "/Users/sjagoe/.local/share/virtualenvs/locust/lib/python3.7/site-packages/haas/haas_application.py", line 115, in <listcomp>
    for start in args.start
  File "/Users/sjagoe/.local/share/virtualenvs/locust/lib/python3.7/site-packages/haas/plugins/discoverer.py", line 214, in discover
    start_filepath, top_level_directory=top_level_directory)
  File "/Users/sjagoe/.local/share/virtualenvs/locust/lib/python3.7/site-packages/haas/plugins/discoverer.py", line 354, in discover_by_file
    top_level_directory)
Message: 'Discovering tests in file: start_filepath=%r, top_level_directory='