GetChecksums when file doesn't exist on any pillar throws an exception

When you perform a GetChecksums command, but the file doesn't exist on any pillar, then the following exception is thrown:
org.bitrepository.common.exceptions.UnableToFinishException: Unable to continue operation, contributors unavailable.

Instead of throwing an exception, this should be handled in a prettier way that doesn't result in a "failing conversation" and cluttering the log files and STOut with exceptions, since this is an expected occurrence.