rptest/util: give check_consistently a distinct error type

Raise ConditionNotHeldError, a subclass of AssertionError, so callers
can catch the specific failure while still treating it as an assertion.

Author: nvartolomei

tests/rptest/tests/util_test.py

@@ -12,7 +12,7 @@
 from ducktape.mark.resource import cluster
 from ducktape.tests.test import Test
 
-from rptest.util import check_consistently, expect_exception
+from rptest.util import ConditionNotHeldError, check_consistently, expect_exception
 
 
 class CheckConsistentlyTest(Test):
@@ -56,7 +56,7 @@ def false_from_start() -> bool:
             calls += 1
             return False
 
-        with expect_exception(AssertionError, lambda _: True):
+        with expect_exception(ConditionNotHeldError, lambda _: True):
             check_consistently(false_from_start, duration_sec=5, interval_sec=0.01)
         assert calls == 1
 
@@ -68,6 +68,11 @@ def flips() -> bool:
             calls += 1
             return calls < 3
 
-        with expect_exception(AssertionError, lambda _: True):
+        with expect_exception(ConditionNotHeldError, lambda _: True):
             check_consistently(flips, duration_sec=5, interval_sec=0.001)
         assert calls == 3
+
+    @cluster(num_nodes=0)
+    def test_check_failure_is_still_an_assertion_error(self) -> None:
+        with expect_exception(AssertionError, lambda _: True):
+            check_consistently(lambda: False, duration_sec=5, interval_sec=0.01)

tests/rptest/util.py

@@ -218,6 +218,12 @@ def wait_until_with_progress_check(
     ) from last_exception
 
 
+class ConditionNotHeldError(AssertionError):
+    """Raised when `check_consistently` observes the checked condition returning false."""
+
+    pass
+
+
 def check_consistently(
     condition: Callable[[], bool],
     duration_sec: float,
@@ -232,7 +238,7 @@ def check_consistently(
     asserts that something good eventually happens (it blocks until a
     condition becomes true), whereas `check_consistently` asserts that nothing
     bad happens (it blocks while the condition *remains* true, raising
-    AssertionError the moment it returns false).
+    `ConditionNotHeldError` the moment it returns false).
 
     `condition` is polled every `interval_sec`; the `duration_sec` window is
     measured from after the first poll, so at least `duration_sec` elapses
@@ -258,7 +264,9 @@ def check_consistently(
     def poll() -> None:
         if not condition():
             msg = err_msg() if callable(err_msg) else err_msg
-            raise AssertionError(msg or f"condition did not hold for {duration_sec}s")
+            raise ConditionNotHeldError(
+                msg or f"condition did not hold for {duration_sec}s"
+            )
 
     poll()
     stop = time.monotonic() + duration_sec