Whether Neymar made the most of it or not is neither here nor there, and whether it was accidental or not the same, there was a collision, it was enough to be a foul, therefore it's a penalty (the only foul in the box that doesn't result in a penalty is obstruction). It's well known that defenders/tackling players will use contact of any sort to try to obstruct/hamper/prevent a player getting a goal-scoring chance/scoring a goal. That equally is cheating, as BigP says. And it's often fine margins.
The other one was a dive, though still a fine margin. And then there were two other situations where a penalty could have been given (plus one to PSG) so it kind of worked out even, and that's with the chasing team being the home team, so overall the officials did pretty well.
PSG had a 4 goal lead, they shouldn't have been letting Barca get close, especially after it went to 3-1. At that stage Barca needed 3 more goals, and the psychological advantage had shifted massively.
That a team of PSG's wealth, experience, and ambitions could allow 3 goals from the 88th minute says much more about three things than about cheating, or officials: PSG should have scored another goal; they shouldn't have let Barca get all those chances in the final minutes; Barca did brilliantly to keep going, and stay in the game. Even to not concede more than one goal under the circumstances was remarkable.
Apart from that, Neymar's goal from the freekick was outstanding, very few players can do that, especially in that sort of situation, when a goal is a must. And as I posted above, the composure of the Barca players for the winning goal, under the circumstances, was worthy of triumphing, PSG's lack of equal composure in defending wasn't.