Attempt to fix 97 (not sure why it's happening to begin with)

apex/__init__.py

@@ -6,9 +6,20 @@ from . import amp
 try:
     from . import optimizers
 except ImportError:
-    print("Warning:  apex was installed without --cuda_ext.  FusedAdam will be unavailable.")
+    # An attempt to fix https://github.com/NVIDIA/apex/issues/97.  I'm not sure why 97 is even
+    # happening because Python modules should only be imported once, even if import is called
+    # multiple times.
+    try:
+        _ = warned_optimizers
+    except NameError:
+        print("Warning:  apex was installed without --cuda_ext.  FusedAdam will be unavailable.")
+        warned_optimizers = True
 try:
     from . import normalization
 except ImportError:
-    print("Warning:  apex was installed without --cuda_ext.  FusedLayerNorm will be unavailable.")
+    try:
+        _ = warned_normalization
+    except NameError:
+        print("Warning:  apex was installed without --cuda_ext.  FusedLayerNorm will be unavailable.")
+        warned_normalization = True
 

apex/parallel/__init__.py

@@ -5,7 +5,11 @@ try:
     import syncbn
     from .optimized_sync_batchnorm import SyncBatchNorm
 except ImportError:
-    print("Warning:  apex was installed without --cuda_ext. Fused syncbn kernels will be unavailable.  Python fallbacks will be used instead.")
+    try:
+        _ = warned_syncbn
+    except NameError:
+        print("Warning:  apex was installed without --cuda_ext. Fused syncbn kernels will be unavailable.  Python fallbacks will be used instead.")
+        warned_syncbn = True
     from .sync_batchnorm import SyncBatchNorm
 
 def convert_syncbn_model(module, process_group=None):

apex/parallel/distributed.py

@@ -4,7 +4,11 @@ try:
     from apex_C import flatten
     from apex_C import unflatten
 except ImportError:
-    print("Warning:  apex was installed without --cpp_ext.  Falling back to Python flatten and unflatten.")
+    try:
+        _ = warned_flatten
+    except NameError:
+        print("Warning:  apex was installed without --cpp_ext.  Falling back to Python flatten and unflatten.")
+        warned_flatten = True
     from torch._utils import _flatten_dense_tensors as flatten
     from torch._utils import _unflatten_dense_tensors as unflatten
 import torch.distributed as dist