feat(dependencies): minimal default tag install (#3362)

tests/optim/test_schedulers.py

@@ -11,6 +11,7 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
+import pytest
 import torch
 from packaging.version import Version
 from torch.optim.lr_scheduler import LambdaLR
@@ -23,8 +24,10 @@ from lerobot.optim.schedulers import (
     save_scheduler_state,
 )
 from lerobot.utils.constants import SCHEDULER_STATE
+from lerobot.utils.import_utils import is_package_available
 
 
+@pytest.mark.skipif(not is_package_available("diffusers"), reason="diffusers not installed")
 def test_diffuser_scheduler(optimizer):
     config = DiffuserSchedulerConfig(name="cosine", num_warmup_steps=5)
     scheduler = config.build(optimizer, num_training_steps=100)