Switch to job protocol

This is really just for MyPy, it was triggering python/mypy#5485

job_runner/coordinator.py

@@ -11,7 +11,7 @@
 from structlog import get_logger
 from job_runner.environment import TrackerEnv, get_environments
 
-from job_runner.tracker import RegisteredJob, RunEnv
+from job_runner.tracker import RegisteredJob
 
 logger = get_logger(__name__)
 

job_runner/tracker.py

@@ -1,15 +1,17 @@
 """Tracking utils for job runner"""
 
-from threading import Event
-from typing import Callable, List, Optional, Union
+from typing import List, Protocol
 from datetime import timedelta
 from dataclasses import dataclass
 from threading import Lock
 
 from .environment import RunEnv
 from .time import AutoTime, read_auto_time
 
-Job = Callable[[RunEnv], None]
+
+class Job(Protocol):
+    def __call__(self, env: RunEnv) -> None:
+        """Call a job with the environment"""
 
 
 @dataclass(frozen=True)