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If the provided checksum does not match actual checksum of the file the pillar should not delete the file and send an end the operation with an error status.
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If a pillar is unable to respond to a certain checksum request it should reject the request with an error. A pillar could be unable to answer such a request because it does not have any files (they the pillar is a checksum pillar) or the specified checksum type is not supported.