Allow worker process to run with --run-time specified, just log a warning about it being ignored

[Sawiq]

As discussed here

[cyberw]

Looks good apart from the type check fail (which probably isnt really your fault, but still needs to be fixed)

[tdadela]

    parts = timespan_regex.match(time_str)
    if not parts:
        raise ValueError("Invalid time span format. Valid formats: 20, 20s, 3m, 2h, 1h20m, 3h30m10s, etc.")
    parts = parts.groupdict()

The same variable name is used for storing two different types.
One of the solutions is simply to rename the parts variable.

Before this PR def parse_timespan(time_str): was untyped so mypy was skipping checking it:
"note: By default the bodies of untyped functions are not checked, consider using --check-untyped-defs"

[cyberw]

Yes that looks terrible. Renaming makes sense I think!

[Sawiq]

I have removed reassignment and called groupdict inline within list comprehension.