Remove use_safetensors from diffusers codebase

[patrickvonplaten]

safetensors is now a required dependency as can be seen here: #4177

This means we can remove all of the following is_safetensors_available codesnippets:

scripts/convert_original_audioldm_to_diffusers.py
41:from diffusers.utils import is_omegaconf_available, is_safetensors_available
827:        if not is_safetensors_available():

src/diffusers/loaders.py
42:    is_safetensors_available,
48:if is_safetensors_available():
178:        if use_safetensors and not is_safetensors_available():
185:            use_safetensors = is_safetensors_available()
590:        if use_safetensors and not is_safetensors_available():
597:            use_safetensors = is_safetensors_available()
807:        if use_safetensors and not is_safetensors_available():
814:            use_safetensors = is_safetensors_available()
1055:        if use_safetensors and not is_safetensors_available():
1062:            use_safetensors = is_safetensors_available()
1389:        use_safetensors = kwargs.pop("use_safetensors", None if is_safetensors_available() else False)

examples/community/checkpoint_merger.py
7:from diffusers.utils import is_safetensors_available
10:if is_safetensors_available():
232:                        if (is_safetensors_available() and checkpoint_path_1.endswith(".safetensors"))
239:                            if (is_safetensors_available() and checkpoint_path_2.endswith(".safetensors"))

src/diffusers/utils/import_utils.py
302:def is_safetensors_available():

src/diffusers/utils/__init__.py
67:    is_safetensors_available,

src/diffusers/pipelines/pipeline_utils.py
55:    is_safetensors_available,
877:        use_safetensors = kwargs.pop("use_safetensors", None if is_safetensors_available() else False)
1169:        if use_safetensors and not is_safetensors_available():
1176:            use_safetensors = is_safetensors_available()

src/diffusers/models/modeling_utils.py
39:    is_safetensors_available,
59:if is_safetensors_available():
303:        if safe_serialization and not is_safetensors_available():
460:        if use_safetensors and not is_safetensors_available():
467:            use_safetensors = is_safetensors_available()

src/diffusers/pipelines/stable_diffusion/convert_from_ckpt.py
51:from ...utils import is_omegaconf_available, is_safetensors_available, logging
1100:        if not is_safetensors_available():
1388:        if not is_safetensors_available():

[chiral-carbon]

Hi! Does this entail that only all occurrences of is_safetensors_available should be cleaned out from the code and the subsequent if statements pertaining to it be removed?
If yes then I'd like to take up this issue as it seems like a very good starting point for contribution.
If it is more complicated than what I have assumed above then feel free to let me know, I'd still love to give it a shot.

[patrickvonplaten]

Sounds great - @DN6 maybe you can help here?

[DN6]

Hi @chiral-carbon. Please go ahead and open a PR for this issue whenever you're ready. Additionally, you may need to update a few tests to reflect your changes. (see issue below)
#4244

I'd be happy to review your PR or answer any questions that you might have.

Thank you for taking the initiative here 🙌🏽

[chiral-carbon]

@DN6 thank you! I will get started on this!

[patrickvonplaten]

@DN6 maybe you could take the PR over here since it seems to have been stalled for a bit too long now

[chiral-carbon]

Hi, I’ll send a PR by the end of the week if you think that timeline works? I was held up due to travel, but I had started on it.
If it is too late tho then I understand, sorry re: the hold up!

[DN6]

Hi @chiral-carbon thanks for your PR. I'll do a review later today.

[peepeepeepoopoopoo]

Is that why I have this error? how do I solve it?