fix torchvision import (#6796)

Author: patrickvonplaten

src/diffusers/training_utils.py

@@ -5,7 +5,7 @@
 
 import numpy as np
 import torch
-from torchvision import transforms
+from transformers import is_torchvision_available
 
 from .models import UNet2DConditionModel
 from .utils import (
@@ -23,6 +23,9 @@
 if is_peft_available():
     from peft import set_peft_model_state_dict
 
+if is_torchvision_available():
+    from torchvision import transforms
+
 
 def set_seed(seed: int):
     """
@@ -79,6 +82,11 @@ def resolve_interpolation_mode(interpolation_type: str):
         `torchvision.transforms.InterpolationMode`: an `InterpolationMode` enum used by torchvision's `resize`
         transform.
     """
+    if not is_torchvision_available():
+        raise ImportError(
+            "Please make sure to install `torchvision` to be able to use the `resolve_interpolation_mode()` function."
+        )
+
     if interpolation_type == "bilinear":
         interpolation_mode = transforms.InterpolationMode.BILINEAR
     elif interpolation_type == "bicubic":