The following line returns an error:
self.m, self.userCodeToUserNameList, self.itemsList, self.userToKeyHash, self.fileToKeyHash = readUserFileMatrixFromFile
Just, use the throw-away variable '_'
self.m, self.userCodeToUserNameList, self.itemsList, self.userToKeyHash, self.fileToKeyHash, _ = readUserFileMatrixFromFile(x,True)
here '_' is deliberately ignored.