fix some flake

Author: francoishernandez

onmt/utils/parse.py

@@ -121,8 +121,8 @@ def validate_train_opts(cls, opt):
             "Number of attention_dropout values must match accum_steps values"
 
         assert not(opt.max_generator_batches > 0 and opt.lambda_cosine != 0), \
-            "-lambda_cosine loss is not implemented for max_generator_batches > 0."
-
+            "-lambda_cosine loss is not implemented " \
+            "for max_generator_batches > 0."
 
     @classmethod
     def validate_translate_opts(cls, opt):