Fix FA2 import + deprecation cycle (#27330)

* put back import

* switch to logger.warnings instead

src/transformers/utils/__init__.py

@@ -117,6 +117,7 @@ from .import_utils import (
     is_essentia_available,
     is_faiss_available,
     is_flash_attn_2_available,
+    is_flash_attn_available,
     is_flax_available,
     is_fsdp_available,
     is_ftfy_available,

src/transformers/utils/import_utils.py

@@ -614,6 +614,14 @@ def is_flash_attn_2_available():
     return _flash_attn_2_available and torch.cuda.is_available()
 
 
+def is_flash_attn_available():
+    logger.warning(
+        "Using `is_flash_attn_available` is deprecated and will be removed in v4.38. "
+        "Please use `is_flash_attn_2_available` instead."
+    )
+    return is_flash_attn_2_available()
+
+
 def is_torchdistx_available():
     return _torchdistx_available