AutoPipelineForText2Image requiring sentencepiece, which isn't a diffusers requirement

[evanscho]

Describe the bug

Importing AutoPipelineForText2Image throws an error if sentencepiece isn't installed, even though sentencepiece is not required for users who just use AutoPipelineForText2Image for SD 1.5 / SD XL and isn't a core diffusers requirement.

Reproduction

git clone --depth 1 https://github.com/huggingface/diffusers &&
cd diffusers &&
git fetch origin 73acebb &&
git reset --hard 73acebb &&
pipenv run pip install .

Then in any python file:
import AutoPipelineForText2Image

Logs

2024-08-01T06:14:56.576275296Z from diffusers import AutoPipelineForText2Image
2024-08-01T06:14:56.576280729Z File "<frozen importlib._bootstrap>", line 1229, in _handle_fromlist
2024-08-01T06:14:56.576285313Z File "/root/.local/share/virtualenvs/api-ORERwo9D/lib/python3.11/site-packages/diffusers/utils/import_utils.py", line 784, in __getattr__
2024-08-01T06:14:56.576364429Z value = getattr(module, name)
2024-08-01T06:14:56.576370913Z ^^^^^^^^^^^^^^^^^^^^^
2024-08-01T06:14:56.576375236Z File "/root/.local/share/virtualenvs/api-ORERwo9D/lib/python3.11/site-packages/diffusers/utils/import_utils.py", line 783, in __getattr__
2024-08-01T06:14:56.576485760Z module = self._get_module(self._class_to_module[name])
2024-08-01T06:14:56.576503570Z ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
2024-08-01T06:14:56.576507880Z File "/root/.local/share/virtualenvs/api-ORERwo9D/lib/python3.11/site-packages/diffusers/utils/import_utils.py", line 795, in _get_module
2024-08-01T06:14:56.576759296Z raise RuntimeError(
2024-08-01T06:14:56.576777586Z RuntimeError: Failed to import diffusers.pipelines.auto_pipeline because of the following error (look up to see its traceback):
2024-08-01T06:14:56.576782880Z Failed to import diffusers.pipelines.kolors.pipeline_kolors_img2img because of the following error (look up to see its traceback):
2024-08-01T06:14:56.576787469Z No module named 'sentencepiece'

System Info

Ubuntu 22.04.4 LTS
Python 3.11.9
Diffusers checkpoint 73acebb

Who can help?

@sayakpaul @yiyixuxu

[yiyixuxu]

thanks! we will fix this