fix: update utils.exponential_backoff to broker in ints only

Python 3.12 finally made good on their promise to start throwing
errors when trying to use `random` with non-ints, so make a good-faith
effort to do that in all versions.

Remove a now-useless test for passing floats that should now be
impossible to hit.

Partial fix for Issue #29

spinach/utils.py

@@ -74,8 +74,8 @@ def exponential_backoff(attempt: int, cap: int=1200) -> timedelta:
     :arg cap: maximum delay, defaults to 20 minutes
     """
     base = 3
-    temp = min(base * 2 ** attempt, cap)
-    return timedelta(seconds=temp / 2 + random.randint(0, temp / 2))
+    temp = min(base * 2 ** attempt, cap) // 2
+    return timedelta(seconds=temp + random.randint(0, temp))
 
 
 @contextlib.contextmanager

tests/test_utils.py

@@ -65,9 +65,6 @@ def func():
 
 
 def test_exponential_backoff():
-    with pytest.raises(ValueError):
-        utils.exponential_backoff(0)
-
     assert (
         timedelta(seconds=3) <= utils.exponential_backoff(1)
         <= timedelta(seconds=6)