[air] Use self-hosted mirror for CIFAR10 dataset (#28480)

The CIFAR10 website host has been unreliable in the past. This PR injects our own mirror into our CI packages for testing.

Signed-off-by: Kai Fricke <kai@anyscale.com>

ci/env/install-dependencies.sh

@@ -421,6 +421,18 @@ install_dependencies() {
     pip install --upgrade tensorflow-probability=="${TFP_VERSION}" tensorflow=="${TF_VERSION}"
   fi
 
+  # Inject our own mirror for the CIFAR10 dataset
+  if [ "${TRAIN_TESTING-}" = 1 ] || [ "${TUNE_TESTING-}" = 1 ] ||  [ "${DOC_TESTING-}" = 1 ]; then
+    SITE_PACKAGES=$(python -c 'from distutils.sysconfig import get_python_lib; print(get_python_lib())')
+    TF_CIFAR="${SITE_PACKAGES}/tensorflow/python/keras/datasets/cifar10.py"
+    TORCH_CIFAR="${SITE_PACKAGES}/torchvision/datasets/cifar.py"
+
+    [ -f "$TF_CIFAR" ] && sed -i 's https://www.cs.toronto.edu/~kriz/cifar-10-python.tar.gz https://air-example-data.s3.us-west-2.amazonaws.com/cifar-10-python.tar.gz g' \
+      "$TF_CIFAR"
+    [ -f "$TORCH_CIFAR" ] &&sed -i 's https://www.cs.toronto.edu/~kriz/cifar-10-python.tar.gz https://air-example-data.s3.us-west-2.amazonaws.com/cifar-10-python.tar.gz g' \
+      "$TORCH_CIFAR"
+  fi
+
   # Additional Tune dependency for Horovod.
   # This must be run last (i.e., torch cannot be re-installed after this)
   if [ "${INSTALL_HOROVOD-}" = 1 ]; then