[gbcdoj]

Papal Coronation Oath, Dating at least to the time of St. Agatho, A.D. 678
"I swear to God Almighty and the Savior Jesus Christ that I will keep whatever has been revealed through Christ and His Successors and whatever the first councils and my predecessors have defined and declared."
"I will keep without sacrifice to itself the discipline and the rite of the Church. I will put outside the Church whoever dares to go against this oath, may it be somebody else or I."

Firstly, the Pope didn't take the Coronation Oath. Secondly, he hasn't put himself out of the Church. Thirdly, he has kept to the discipline and rite of the Church - unless you think St. Pius V also excommunicated himself:

We decided to entrust this work to learned men of our selection. They very carefully collated all their work with the ancient codices in Our Vatican Library and with reliable, preserved or emended codices from elsewhere. Besides this, these men consulted the works of ancient and approved authors concerning the same sacred rites; and thus they have restored the Missal itself to the original form and rite of the holy Fathers ... This new rite alone is to be used ... (Quo Primum)

[Maximilian]

Firstly, the Pope didn't take the Coronation Oath.

Do you have a definitive source for this statement? I have heard this bandied about, but I have never seen conclusive documentation. I've strongly wondered whether this were really true, and you state it rather categorically, as if you're certain of the facts.

Does this also apply to Pope Paul VI and/or John Paul I?