Raise when CUDA not installed

src/hf_kernels/utils.py

@@ -23,6 +23,9 @@ CACHE_DIR: Optional[str] = os.environ.get("HF_KERNELS_CACHE", None)
 def build_variant():
     import torch
 
+    if torch.version.cuda is None:
+        raise AssertionError("This kernel requires CUDA to be installed. Torch was not compiled with CUDA enabled.")
+
     torch_version = parse(torch.__version__)
     cuda_version = parse(torch.version.cuda)
     cxxabi = "cxx11" if torch.compiled_with_cxx11_abi() else "cxx98"
@@ -50,9 +53,8 @@ def install_kernel(
     repo_id: str, revision: str, local_files_only: bool = False
 ) -> Tuple[str, str]:
     """Download a kernel for the current environment to the cache."""
-    package_name = get_metadata(repo_id, revision, local_files_only=local_files_only)[
-        "torch"
-    ]["name"]
+    package_name = repo_id.split('/')[-1]
+    package_name = package_name.replace('-', '_')
     repo_path = snapshot_download(
         repo_id,
         allow_patterns=f"build/{build_variant()}/*",