new method to handle waiting

glean-core/python/tests/metrics/test_timing_distribution.py

@@ -162,13 +162,20 @@ def test_measure():
     )
 
     with metric.measure():
-        time.sleep(0.1)
+        iteration_guard = 10**8  # this guard should be
+        # about 100 times as long as the loop
+        iterations = 0
+        end_time = time.perf_counter() + 0.1
+        while time.perf_counter() < end_time:
+            if iterations > iteration_guard:
+                raise Exception("Loop to accrue time exceeded guard")
+            iterations += 1
 
     snapshot = metric.test_get_value()
     # more than 0.1s = 100ms = 10^8 nanoseconds
     # less than 0.2s = 200ms = 2*10^8 nanoseconds
-    assert 10**8 < snapshot.sum
-    assert 2 * 10**8 > snapshot.sum
+    assert snapshot.sum > 10**8, "Measured value below minimum time"
+    assert snapshot.sum < 2 * 10**8, "Measured value above maximum time"
 
 
 def test_measure_exception():