Question: When did the accident occur that the 2017 Joan Gamper Trophy held a tribute for?
Sentence (from "2017 Joan Gamper Trophy"): This marked Chapecoense's first ever appearance in the Joan Gamper Trophy, as a tribute to the 71 Chapecoense players and staff who lost their lives after the LaMia Flight 2933 tragedy in La Unión, Colombia, on 28 November 2016.
Relevant evidence: Yes