fix glide import error

src/diffusers/pipelines/__init__.py

 from .pipeline_bddm import BDDM
 from .pipeline_ddim import DDIM
 from .pipeline_ddpm import DDPM
-from .pipeline_glide import GLIDE
+try:
+    from .pipeline_glide import GLIDE
+except ImportError:
+    class GLIDE:
+        pass
 from .pipeline_latent_diffusion import LatentDiffusion
 from .pipeline_pndm import PNDM

src/diffusers/pipelines/pipeline_glide.py

@@ -15,6 +15,7 @@
 """ PyTorch CLIP model."""
 
 import math
+import logging
 from dataclasses import dataclass
 from typing import Any, Optional, Tuple, Union