You tell the truth and are open all along the line. This is THE ONLY hope, because you will be on record with Canadian immigration, and it is entirely possible that this past history could come to the notice of INZ. Even if it happened not to arise while first processing your application, if it afterwards did so, the fact that you had not disclosed the situation would be regarded as fraud, the visa issued on the basis of the fraud would be cancelled, and you would find yourself with another exclusion.