ran `arc unit --everything` from project root and also ran it from
a sub-directory.
```
$ arc unit --everything
PASS 1ms★ test_log.FilterTest.test_filter_can_invert_behavior
PASS 1ms★ test_log.FilterTest.test_filter_filters_matching
PASS <1ms★ test_log.FilterTest.test_filter_filters_matching_lambda
PASS 1ms★ test_log.FilterTest.test_filter_filters_matching_regex
PASS 3ms★ test_log.FilterTest.test_filter_loads
PASS 2ms★ test_log.FilterTest.test_filter_loads_filters_correctly
PASS <1ms★ test_log.FilterTest.test_filter_loads_supports_numeric_comparisons
PASS 1ms★ test_log.FilterTest.test_filter_parse
PASS 1ms★ test_log.JSONFormatterTest.test_format_includes_all_serializable_logrecord_fields
PASS 1ms★ test_log.JSONFormatterTest.test_format_includes_exceptions_as_text
PASS <1ms★ test_log.JSONFormatterTest.test_format_includes_extra_fields
PASS 1ms★ test_log.JSONFormatterTest.test_make_record
PASS 1ms★ test_nrpe.NRPETest.test_load
PASS <1ms★ test_nrpe.NRPETest.test_registered_check
PASS <1ms★ test_nrpe.NRPETest.test_unregistered_check
PASS <1ms★ test_ssh.JSONOutputHandlerTest.test_accept_ignores_bad_json
PASS <1ms★ test_ssh.JSONOutputHandlerTest.test_accept_parses_and_logs_json_messages
PASS <1ms★ test_ssh.JSONOutputHandlerTest.test_lines_buffers_partial_lines
PASS 4ms★ test_checks.ChecksConfigTest.test_custom_type
PASS 2ms★ test_checks.ChecksConfigTest.test_load_bad_type
PASS 5ms★ test_checks.ChecksConfigTest.test_load_valid_config
PASS 19ms★ test_checks.ChecksExecuteTest.test_execute
PASS 222ms test_checks.ChecksExecuteTest.test_execute_concurrency
PASS 18ms★ test_checks.ChecksExecuteTest.test_execute_failure
PASS 15ms★ test_checks.ChecksExecuteTest.test_execute_timeout
PASS <1ms★ test_utils.UtilsTest.test_check_php_opening_tag
PASS 3ms★ test_utils.UtilsTest.test_check_target_hosts
PASS 1ms★ test_utils.UtilsTest.test_check_valid_json_file
PASS <1ms★ test_utils.UtilsTest.test_get_env_specific_filename
```