@ptrblck, similar to @naveenvemy, I observed that this warning occurs when loading the fashion-MNIST dataset as follows:
def load_data():
    transform = tv.transforms.ToTensor()

    training_data = tv.datasets.FashionMNIST(dataset_path,
                                             train=True,
                                             download=True,
                                             transform=transform)
    test_data = tv.datasets.FashionMNIST(dataset_path,
                                         train=False,
                                         download=True,
                                         transform=transform)

    return training_data, test_data

What is interesting is that the warning doesn’t occur with torch 1.8.1 + torchvision 0.9.1, but does occur with torch 1.9.0 + torchvision 0.10.0.
I tried to fix it as follows, but it didn’t work:
# Fix given NumPy array is not writeable warning
class ToTensor(tv.transforms.ToTensor):

    def __call__(self, pic):
        return super().__call__(np.array(pic, copy=True))

Do you have any suggestions?