Use https for dataset download URLs where the host supports TLS

[fjankovi]

Several dataset classes download over plain http://. Where the host serves the same bytes over TLS, this switches them to https://.

Changed

Dataset	Host	Verification
Food101	data.vision.ee.ethz.ch	200, full Content-Length
STL10	ai.stanford.edu	200, full Content-Length
SEMEION	archive.ics.uci.edu	MD5 matches pinned cb545d37…
MovingMNIST	www.cs.toronto.edu	200, full Content-Length
Places365	data.csail.mit.edu	both devkit MD5s match pinned
KMNIST	codh.rois.ac.jp	all 4 MD5s match pinned (http already 301'd here)
FashionMNIST	S3	all 4 MD5s match pinned

FashionMNIST is not a scheme swap. It pointed at the S3 website endpoint (fashion-mnist.s3-website.eu-central-1.amazonaws.com), which is HTTP-only by design — S3 website endpoints do not support TLS. This points it at the REST endpoint for the same bucket (fashion-mnist.s3.eu-central-1.amazonaws.com), which does.

Every changed URL was fetched over https and checked against the checksum already pinned in the source. The small ones match exactly; the multi-GB archives were confirmed by request rather than downloaded in full.

Deliberately not changed

Three hosts cannot serve https, and rewriting them turns a working download into a hostname-verification failure. A short comment now records why, so the next sweep doesn't complete them:

Host	Dataset	Why
yann.lecun.com	MNIST	connections to port 443 are refused — no TLS listener
ufldl.stanford.edu	SVHN	certificate is valid only for ai.stanford.edu (SAN mismatch)
shuoyang1213.me	WIDERFace	certificate is for *.github.com (SAN mismatch)

All three remain checksummed. Note MNIST's yann.lecun.com entry is the fallback mirror — https://ossci-datasets.s3.amazonaws.com/mnist/ is tried first — and it now returns 404 for the four resource files regardless of scheme, so test_url_is_accessible[MNIST, …] already fails on main. That's pre-existing and out of scope here; happy to open a separate issue.

LFW, PhotoTour and SUN397 are also left alone: those hosts no longer resolve (vis-www.cs.umass.edu and icvl.ee.ic.ac.uk are NXDOMAIN) or 404 on both schemes. Already tracked in #9580, #8711, #9002 and #9348.

Testing

test/test_datasets_download.py, run against the patched tree:

26 passed  — FashionMNIST 4/4, KMNIST 4/4, SEMEION, STL10, Places365 2/2,
              EMNIST, QMNIST 6/6, SVHN 3/3, WIDERFace 4/4
 4 failed  — MNIST / yann.lecun.com (identical failure on pristine main; see above)

MovingMNIST and Food101 have no fixture in that file, so they were verified by direct request.

No behaviour change beyond the URLs; all checksums are untouched.

[pytorch-bot]

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