use importlib instead of deprecated imp module

[rathann]

This fixes tests with python 3.12 where the imp module was removed.

This should fix issue #74.

[wbond]

I've tried a few implementations, but the new importlib API is far more complex, so it will require some more work to get it right.

[wbond]

@rathann Can you test out this version on 3.12? I'd try python run.py tests and python run.py ci

[rathann]

@wbond thanks a lot for working on this. python run.py tests passes, but python run.py ci fails with:

$ python3 run.py ci
Traceback (most recent call last):
  File "/builddir/build/BUILD/oscrypto-1.3.0/run.py", line 8, in <module>
    run_task()
  File "/builddir/build/BUILD/oscrypto-1.3.0/dev/_task.py", line 134, in run_task
    task_mod = _import_from('dev.%s' % task, package_root, allow_error=True)
               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/builddir/build/BUILD/oscrypto-1.3.0/dev/_import.py", line 80, in _import_from
    spec.loader.exec_module(module)
  File "<frozen importlib._bootstrap_external>", line 994, in exec_module
  File "<frozen importlib._bootstrap>", line 400, in _call_with_frames_removed
  File "/builddir/build/BUILD/oscrypto-1.3.0/dev/ci.py", line 24, in <module>
    from .coverage import run as run_coverage
  File "/builddir/build/BUILD/oscrypto-1.3.0/dev/coverage.py", line 7, in <module>
    import imp
ModuleNotFoundError: No module named 'imp'

Looks like we missed at least one instance of imp usage.

[rathann]

This fixes run.py ci on 3.12 for me, but it looks like it's still failing the CircleCI tests.