def cant_trace_msg(concurrency: str, the_module: ModuleType | None) -> str | None:
    """What might coverage.py say about a concurrency setting and imported module?"""
    # In the concurrency choices, "multiprocessing" doesn't count, so remove it.
    if "multiprocessing" in concurrency:
        parts = concurrency.split(",")
        parts.remove("multiprocessing")
        concurrency = ",".join(parts)

    if the_module is None:
        # We don't even have the underlying module installed, we expect
        # coverage to alert us to this fact.
        expected_out = (
            f"Couldn't trace with concurrency={concurrency}, the module isn't installed.\n"
        )
    elif testenv.C_TRACER or concurrency == "thread" or concurrency == "":
        expected_out = None
    else:
        expected_out = (
            f"Can't support concurrency={concurrency} with PyTracer, only threads are supported.\n"
        )
    return expected_out
What might coverage.py say about a concurrency setting and imported module?
tests/test_concurrency.py