update Loggers (#818)

* add warnings

* fix link

README.md

@@ -295,7 +295,7 @@ Lightning also adds a text column with all the hyperparameters for this experime
 
 - [Running grid search on a cluster](https://pytorch-lightning.rtfd.io/en/latest/pytorch_lightning.trainer.distrib_data_parallel.html)  
 - [Fast dev run](https://pytorch-lightning.rtfd.io/en/latest/pytorch_lightning.utilities.debugging.html)
-- [Logging](https://pytorch-lightning.rtfd.io/en/latest/pytorch_lightning.logging.html)
+- [Logging](https://pytorch-lightning.rtfd.io/en/latest/pytorch_lightning.loggers.html)
 - [Implement Your Own Distributed (DDP) training](https://pytorch-lightning.rtfd.io/en/latest/pytorch_lightning.core.lightning.html#pytorch_lightning.core.lightning.LightningModule.configure_ddp)
 - [Multi-GPU & Multi-node](https://pytorch-lightning.rtfd.io/en/latest/pytorch_lightning.trainer.distrib_parts.html)
 - [Training loop](https://pytorch-lightning.rtfd.io/en/latest/pytorch_lightning.trainer.training_loop.html)

pytorch_lightning/loggers/neptune.py

@@ -12,7 +12,8 @@ from logging import getLogger
 try:
     import neptune
 except ImportError:
-    raise ImportError('Missing neptune package. Run `pip install neptune-client`')
+    raise ImportError('You want to use `neptune` logger which is not installed yet,'
+                      ' please install it e.g. `pip install neptune-client`.')
 
 from torch import is_tensor
 

pytorch_lightning/loggers/wandb.py

@@ -11,7 +11,8 @@ import os
 try:
     import wandb
 except ImportError:
-    raise ImportError('Missing wandb package.')
+    raise ImportError('You want to use `wandb` logger which is not installed yet,'
+                      ' please install it e.g. `pip install wandb`.')
 
 from .base import LightningLoggerBase, rank_zero_only