Transformers version req for UnCLIP (#1766)

* Transformers version req for UnCLIP

* add to the list

src/diffusers/pipelines/unclip/__init__.py

-from ...utils import is_torch_available, is_transformers_available
+from ...utils import (
+    OptionalDependencyNotAvailable,
+    is_torch_available,
+    is_transformers_available,
+    is_transformers_version,
+)
 
 
-if is_transformers_available() and is_torch_available():
+try:
+    if not (is_transformers_available() and is_torch_available() and is_transformers_version(">=", "4.25.0")):
+        raise OptionalDependencyNotAvailable()
+except OptionalDependencyNotAvailable:
+    from ...utils.dummy_torch_and_transformers_objects import UnCLIPPipeline
+else:
     from .pipeline_unclip import UnCLIPPipeline
-    from .text_proj import UnCLIPTextProjModel

src/diffusers/utils/import_utils.py

@@ -359,6 +359,7 @@ def requires_backends(obj, backends):
         "VersatileDiffusionPipeline",
         "VersatileDiffusionDualGuidedPipeline",
         "StableDiffusionImageVariationPipeline",
+        "UnCLIPPipeline",
     ] and is_transformers_version("<", "4.25.0"):
         raise ImportError(
             f"You need to install `transformers>=4.25` in order to use {name}: \n```\n pip install"