Warning message for FusedAdam import if unavailable

apex/__init__.py

@@ -3,4 +3,7 @@
 from . import fp16_utils
 from . import parallel
 from . import amp
-from . import optimizers
+try:
+    from . import optimizers
+except ImportError:
+    print("Warning:  apex was installed without --cuda_ext.  FusedAdam will be unavailable.")

apex/parallel/__init__.py

@@ -3,10 +3,9 @@ import torch
 from .distributed import DistributedDataParallel, Reducer
 try:
     import syncbn
-    print("using fused syncBN")
     from .optimized_sync_batchnorm import SyncBatchNorm
 except ImportError:
-    print("using non-fused syncBN, try install apex with 'python setup.py install --cuda_ext' to enable fused syncBN for better performance")
+    print("Warning:  apex was installed without --cuda_ext. Fused syncbn kernels will be unavailable.  Python fallbacks will be used instead.")
     from .sync_batchnorm import SyncBatchNorm
 
 def convert_syncbn_model(module):

apex/parallel/distributed.py

@@ -4,7 +4,7 @@ try:
     from apex_C import flatten
     from apex_C import unflatten
 except ImportError:
-    print("Apex was built without --cpp_ext; falling back to Python flatten and unflatten")
+    print("Warning:  apex was installed without --cpp_ext.  Falling back to Python flatten and unflatten.")
     from torch._utils import _flatten_dense_tensors as flatten
     from torch._utils import _unflatten_dense_tensors as unflatten
 import torch.distributed as dist