fix libnat imports

Summary: Bring back the changes in D17661768

Reviewed By: ailzhang

Differential Revision: D17920299

fbshipit-source-id: be3f93a044a8710c8b475012c39e36a3e6507fad

fairseq/models/insertion_transformer.py

@@ -6,7 +6,6 @@
 import numpy as np
 import torch
 import torch.nn.functional as F
-from fairseq import libnat
 from fairseq.utils import new_arange
 from fairseq.models import register_model, register_model_architecture
 from fairseq.models.levenshtein_transformer import (
@@ -52,6 +51,13 @@ neg_scorer = NegativeDistanceScore()
 
 
 def _get_ins_targets(in_tokens, out_tokens, padding_idx, unk_idx, vocab_size, tau=None):
+    try:
+        from fairseq import libnat
+    except ImportError as e:
+        import sys
+        sys.stderr.write('ERROR: missing libnat. run `pip install --editable .`\n')
+        raise e
+
     B = in_tokens.size(0)
     T = in_tokens.size(1)
     V = vocab_size

fairseq/models/levenshtein_transformer.py

@@ -5,7 +5,6 @@
 
 import torch
 import torch.nn.functional as F
-from fairseq import libnat
 from fairseq.utils import new_arange
 from fairseq.models import register_model, register_model_architecture
 from fairseq.models.model_utils import fill_tensors as _fill, skip_tensors as _skip
@@ -19,6 +18,13 @@ from fairseq.modules.transformer_sentence_encoder import init_bert_params
 
 
 def _get_ins_targets(in_tokens, out_tokens, padding_idx, unk_idx):
+    try:
+        from fairseq import libnat
+    except ImportError as e:
+        import sys
+        sys.stderr.write('ERROR: missing libnat. run `pip install --editable .`\n')
+        raise e
+
     in_seq_len, out_seq_len = in_tokens.size(1), out_tokens.size(1)
 
     with torch.cuda.device_of(in_tokens):
@@ -61,6 +67,13 @@ def _get_ins_targets(in_tokens, out_tokens, padding_idx, unk_idx):
 
 
 def _get_del_targets(in_tokens, out_tokens, padding_idx):
+    try:
+        from fairseq import libnat
+    except ImportError as e:
+        import sys
+        sys.stderr.write('ERROR: missing libnat. run `pip install --editable .`\n')
+        raise e
+
     out_seq_len = out_tokens.size(1)
 
     with torch.cuda.device_of(in_tokens):
@@ -87,6 +100,13 @@ def _get_del_targets(in_tokens, out_tokens, padding_idx):
 
 
 def _get_del_ins_targets(in_tokens, out_tokens, padding_idx):
+    try:
+        from fairseq import libnat
+    except ImportError as e:
+        import sys
+        sys.stderr.write('ERROR: missing libnat. run `pip install --editable .`\n')
+        raise e
+
     in_seq_len, out_seq_len = in_tokens.size(1), out_tokens.size(1)
 
     with torch.cuda.device_of(in_tokens):