Hogwarts didn't always have bathrooms. Before adopting Muggle plumbing methods in the eighteenth century, witches and wizards simply relieved themselves wherever they stood, and vanished the evidence.
Let me repeat that tweet just in case you didn’t read it properly...
This is from the official Pottermore account!!!
As you can imagine, Harry Potter fans, and pretty much all of Twitter, was wondering if this was a legit tweet.
Well I guess 2019 is off to a good start now that we know this! Cheers!!