The following code is in test_runner.py:
# Individual tests have been specified. Run specified tests that exist
# in the ALL_SCRIPTS list. Accept the name with or without .py extension.
tests = [re.sub("\.py$", "", test) + ".py" for test in tests]
This adds .py to the end of the test name, making it impossible to run, say rpc_bind.py --ipv6. This test was failing here locally so I wanted to run it separately.
I think this step should be skipped if .py is already given.
Or alternatively, only applied to the first part of the test name and not arguments.