Log Message:
py-pebble: update to 5.0.3.

5.0.3

Fixes:
 - issue #111: reinstate `Pool.schedule` function in place of
   `Pool.submit`.

5.0.2

Fixes:
 - issue #108: fix build tag enforcing Python 3.6 as minimum
   compatible version.

5.0.1

Improvements:
 - issue #105: run callbacks after process termination on timeout or
   task cancellation

5.0.0

Backward incompatible changes:
 - issue #93: Python 2 is no longer compatible. Minimum supported
   version is now 3.7.

Deprecations:
 - issue #90: pools `schedule` method is now deprecated, use `submit`
   instead.

Features:
 - issue #90: pools are now compatible with asyncio APIs.
 - issue #94: asynchronous function decorators
 - issue #102: type hints have been added to all functionalities
 - issue #103: support alternative multiprocessing.context
   implementations

Fixes:
 - issue #99: fix deadlock when closing a full pipe on Windows in pool