SSA-6324: proof of concept -- running tests in Docker container. These tests all pass at the pytest command line -AND- inside a  container. scode project updater code removed -- doesn't work, and will be merged in from archive eventually.

SSA-6324: All tests pass when run locally. In Docker container, tests that exercise the CLI all fail, unable to find the "datafetcher" entry_point.

SSA-6324: tests pass when run locally; some fail in Docker container. Committing what I've got so as not to lose it after tearing my hair out for a day and a half.

SSA-6324: placate Pylint somewhat; this time -really- get rid of the properties file after the Docker image is built; look what Pathlib can do!

SSA-6324: pytest on datafetcher_test.py executes in a Docker container. capo properties file is copied to the docker build directory, then deleted.