Fix torch.hub to not depend on libnat

Summary: Pull Request resolved: fairinternal/fairseq-py#878

Differential Revision: D17661768

Pulled By: myleott

fbshipit-source-id: 1e4c5f09eb14c40d491ca2459fd2adb8382fb6d2

Author: Myle Ott

fairseq/models/insertion_transformer.py

@@ -6,7 +6,7 @@
 import numpy as np
 import torch
 import torch.nn.functional as F
-from fairseq import libnat
+
 from fairseq.models import register_model, register_model_architecture
 from fairseq.models.levenshtein_transformer import (
     LevenshteinTransformerDecoder,
@@ -51,6 +51,13 @@ def compute_score_full(self, L, tau):
 
 
 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 +5,7 @@
 
 import torch
 import torch.nn.functional as F
-from fairseq import libnat
+
 from fairseq.models import register_model, register_model_architecture
 from fairseq.models.model_utils import fill_tensors as _fill, skip_tensors as _skip
 from fairseq.models.transformer import (
@@ -18,6 +18,13 @@
 
 
 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):
@@ -60,6 +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):
@@ -86,6 +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):