prepare RC0 (#8399)

* RC0

* Update changelog

Co-authored-by: Kaushik B <[email protected]>
Co-authored-by: Kaushik B <[email protected]>

Author: Borda

CHANGELOG.md

@@ -166,6 +166,9 @@ The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/).
 - Added support for `accelerator='cpu'|'gpu'|'tpu'|'ipu'|'auto'` ([#7808](https://github.com/PyTorchLightning/pytorch-lightning/pull/7808))
 
 
+- Added `tpu_spawn_debug` to plugin registry ([#7933](https://github.com/PyTorchLightning/pytorch-lightning/pull/7933))
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 - Enabled traditional/manual launching of DDP processes through `LOCAL_RANK` and `NODE_RANK` environment variable assignments ([#7480](https://github.com/PyTorchLightning/pytorch-lightning/pull/7480))
 
 
@@ -303,6 +306,12 @@ The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/).
 - `Trainer(resume_from_checkpoint=...)` now restores the model directly after `LightningModule.setup()`, which is before `LightningModule.configure_sharded_model()` ([#7652](https://github.com/PyTorchLightning/pytorch-lightning/pull/7652))
 
 
+- Moved `torch.cuda.set_device()` to enable collective calls earlier in setup ([#8312](https://github.com/PyTorchLightning/pytorch-lightning/pull/8312))
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+- Use XLA utility API to move data to CPU (Single TPU core) ([#8078](https://github.com/PyTorchLightning/pytorch-lightning/pull/8078))
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 ### Deprecated
 
 
@@ -460,6 +469,9 @@ The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/).
 - Fixed missing call to `LightningModule.untoggle_optimizer` in training loop when running gradient accumulation with multiple optimizers ([#8284](https://github.com/PyTorchLightning/pytorch-lightning/pull/8284))
 
 
+- Fixed progress bar updates for Pod Training ([#8258](https://github.com/PyTorchLightning/pytorch-lightning/pull/8258))
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 ## [1.3.8] - 2021-07-01
 
 ### Fixed

pytorch_lightning/__about__.py

@@ -1,7 +1,7 @@
 import time
 
 _this_year = time.strftime("%Y")
-__version__ = '1.4.0dev'
+__version__ = '1.4.0rc0'
 __author__ = 'William Falcon et al.'
 __author_email__ = '[email protected]'
 __license__ = 'Apache-2.0'