actions: do not ignore test results

[asher-m]

Test results are effectively ignored because of the configuration of CI/CD workflows.

Presently, the workflow responsible for running the tests is dotted with

continue-on-error: true

which allows the workflow to continue even if the step fails (at least the step where continue-on-error: true was set).

Additionally, flake8 is run as

flake8 . --count --select=E9,F63,F7,F82 --show-source --statistics
flake8 . --count --exit-zero --max-complexity=10 --max-line-length=127 --statistics

where --exit-zero causes flake8 to terminate without error, despite the presence of linting errors in the code.

Suggestion

1. Remove continue-on-error: true everywhere except where its presence makes sense, (coveralls.io test coverage reporting only, most likely).
2. Remove --exit-zero from flake8

Unfortunately, these changes will cause CI/CD to fail—but they will do so correctly with the desired behavior, rather than silently allowing failing code to pass.