module 'select' has no attribute 'poll' on Mac OS Python 3.8

[jharriman]

Using version 2.1.1 of mirakuru on Python 3.8.0 on Mac OS

$ pip freeze | grep mirakuru
mirakuru==2.1.1

It's easy to reproduce the error:

Python 3.8.0 (default, Dec 18 2019, 02:11:36) 
[Clang 11.0.0 (clang-1100.0.33.12)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> import mirakuru
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/Users/justyn/go/src/github.com/jharriman/carbyn-transit/transitparse/venv/lib/python3.8/site-packages/mirakuru/__init__.py", line 24, in <module>
    from mirakuru.output import OutputExecutor
  File "/Users/justyn/go/src/github.com/jharriman/carbyn-transit/transitparse/venv/lib/python3.8/site-packages/mirakuru/output.py", line 33, in <module>
    class OutputExecutor(SimpleExecutor):
  File "/Users/justyn/go/src/github.com/jharriman/carbyn-transit/transitparse/venv/lib/python3.8/site-packages/mirakuru/output.py", line 136, in OutputExecutor
    def _wait_for_output(self, *polls: Tuple[select.poll, IO[Any]]) -> bool:
AttributeError: module 'select' has no attribute 'poll'

It looks like there's been previous work before in #331, but that change did not properly fix the type annotations for def _wait_for_output(self, *polls: Tuple[select.poll, IO[Any]]). Likely the fix is as simple as adding quotes around select.poll.