add rank warning (#1428)

* add rank warning

* changelog

* use rank_zero_warn

* user trainer_init

* replace warnings

* fix test

* flake8

* docs

* changelog

* bug lol

pytorch_lightning/trainer/training_loop.py

@@ -133,7 +133,6 @@ in your model.
 """
 
 import copy
-import warnings
 from abc import ABC, abstractmethod
 from typing import Callable
 from typing import Union, List
@@ -148,6 +147,7 @@ from pytorch_lightning.loggers import LightningLoggerBase
 from pytorch_lightning.overrides.data_parallel import LightningDistributedDataParallel, LightningDataParallel
 from pytorch_lightning.utilities.exceptions import MisconfigurationException
 from pytorch_lightning.trainer.supporters import TensorRunningAccum
+from pytorch_lightning.utilities import rank_zero_warn
 
 try:
     from apex import amp
@@ -284,8 +284,8 @@ class TrainerTrainLoopMixin(ABC):
         """Warning: this is just empty shell for code implemented in other class."""
 
     def train(self):
-        warnings.warn('Displayed epoch numbers in the progress bar start from "1" until v0.6.x,'
-                      ' but will start from "0" in v0.8.0.', RuntimeWarning)
+        rank_zero_warn('Displayed epoch numbers in the progress bar start from "1" until v0.6.x,'
+                       ' but will start from "0" in v0.8.0.', RuntimeWarning)
 
         # get model
         model = self.get_model()
@@ -750,8 +750,8 @@ class TrainerTrainLoopMixin(ABC):
             with self.profiler.profile('training_end'):
                 output = model_ref.training_end(output)
 
-            warnings.warn('`training_end` was deprecated in 0.7.0 and will be removed 1.0.0.'
-                          ' Use training_epoch_end instead', DeprecationWarning)
+            rank_zero_warn('`training_end` was deprecated in 0.7.0 and will be removed 1.0.0.'
+                           ' Use training_epoch_end instead', DeprecationWarning)
 
         return output