Use more specific assert error string

Signed-off-by: Mathias L. Baumann <[email protected]>

Author: Marenz

src/frequenz/sdk/actor/power_distributing/_distribution_algorithm/_distribution_algorithm.py

@@ -55,7 +55,7 @@ def __init__(self, batteries: list[BatteryData]) -> None:
         Args:
             batteries: The batteries to aggregate.
         """
-        assert len(batteries) > 0, "No batteries given."
+        assert len(batteries) > 0, "AggregatedBatteryData: No batteries given."
 
         # We need only one component ID for DistBatteryData to be able to
         # identify the pair