Can you tell me the article of the Constitution that says you have to do a Yes/No referendum to call the election of the Constituent Assembly?
The discussion is getting off-topic, but I'll say this:
Artículo 347. El pueblo de Venezuela es el depositario del poder constituyente originario. En ejercicio de dicho poder, puede convocar una Asamblea Nacional Constituyente con el objeto de transformar al Estado, crear un nuevo ordenamiento jurídico y redactar una nueva Constitución.
"The people of Venezuela may invoke a Constituent Assembly".
Artículo 348. La iniciativa de convocatoria a la Asamblea Nacional Constituyente podrá hacerla el Presidente...
"The
initiative to convoke a Constituent Assembly may be enforced by the President..."
Seriously, try to find any Venezuelan lawyer with experience in Constitutional law. All of them will agree that this "initiative to convoke" means that it has to be approved by the people first (like Article 347 says). If Maduro is so fond of democracy, why didn't he ask the people if they wanted a Constituent Assembly? There was no way to vote against the Constituent Assembly.
In short,
the petro is illegal, by international consensus, which is all that matters when you're trying to raise money. Venezuela's own sovereign Parliament and 12 countries in the Americas have refused to recognize the authority of a supra-constitutional body that sits on top of democratic institutions.