Add run on cpu-only compatibility

lerobot/scripts/train.py

@@ -1,4 +1,5 @@
 import logging
+import warnings
 
 import hydra
 import numpy as np
@@ -115,7 +116,11 @@ def train(cfg: dict, out_dir=None, job_name=None):
 
     init_logging()
 
-    assert torch.cuda.is_available()
+    if cfg.device == "cuda":
+        assert torch.cuda.is_available()
+    else:
+        warnings.warn("Using CPU, this will be slow.", UserWarning, stacklevel=1)
+
     torch.backends.cudnn.benchmark = True
     torch.backends.cuda.matmul.allow_tf32 = True
     set_seed(cfg.seed)