hotfix: mock examples (#6632)

* mock examples

* drop from GA

azure-pipelines.yml

@@ -121,4 +121,6 @@ jobs:
         # cd pl_examples/basic_examples
         # bash submit_ddp_job.sh
         # bash submit_ddp2_job.sh
+      env:
+        PL_USE_MOCKED_MNIST: "1"
       displayName: 'Examples'

pl_examples/__init__.py

@@ -15,10 +15,10 @@ _PACKAGE_ROOT = os.path.dirname(_EXAMPLES_ROOT)
 _DATASETS_PATH = os.path.join(_PACKAGE_ROOT, 'Datasets')
 
 _TORCHVISION_AVAILABLE = _module_available("torchvision")
-_TORCHVISION_MNIST_AVAILABLE = True
+_TORCHVISION_MNIST_AVAILABLE = not bool(os.environ.get("PL_USE_MOCKED_MNIST", False))
 _DALI_AVAILABLE = _module_available("nvidia.dali")
 
-if _TORCHVISION_AVAILABLE:
+if _TORCHVISION_MNIST_AVAILABLE:
     try:
         from torchvision.datasets.mnist import MNIST
         MNIST(_DATASETS_PATH, download=True)