I have accumulated all the documents, except one, for my permanent residency application. I was picked for this through Express Entry. The missing document is a police certificate, which is in pending state with a ETA that isn't provided yet. I need to submit my application in two weeks. In the worst case scenario that I don't receive the police certificate in time, is it possible to submit this piece of document with a letter of explanation and an attachment showing the state of my police certificate?