Fix load_dataset signature (#1281)

Summary:
Fix for https://github.com/pytorch/fairseq/issues/1240
Tested with MaskedLMTask.
Pull Request resolved: https://github.com/pytorch/fairseq/pull/1281

Differential Revision: D18051472

fbshipit-source-id: 0aeff60c71489655f5e621349f780ba9cd8c027a

fairseq/tasks/masked_lm.py

@@ -71,7 +71,7 @@ class MaskedLMTask(FairseqTask):
         print('| dictionary: {} types'.format(len(dictionary)))
         return cls(args, dictionary)
 
-    def load_dataset(self, split, epoch=0, combine=False):
+    def load_dataset(self, split, epoch=0, combine=False, **kwargs):
         """Load a given dataset split.
 
         Args:

fairseq/tasks/multilingual_masked_lm.py

@@ -110,7 +110,7 @@ class MultiLingualMaskedLMTask(FairseqTask):
         smoothed_prob = smoothed_prob / smoothed_prob.sum()
         return smoothed_prob
 
-    def load_dataset(self, split, epoch=0, combine=False):
+    def load_dataset(self, split, epoch=0, combine=False, **kwargs):
         """Load a given dataset split.
 
         Args: