fix missing return statement. Do not normalize remote paths

pytorch_lightning/callbacks/model_checkpoint.py

@@ -289,7 +289,8 @@ def on_train_start(self, trainer, pl_module):
         self.dirpath = ckpt_path
 
         assert trainer.global_rank == 0, 'tried to make a checkpoint from non global_rank=0'
-        os.makedirs(self.dirpath, exist_ok=True)
+        if not gfile.exists(self.dirpath):
+            makedirs(self.dirpath)
 
     @rank_zero_only
     def on_validation_end(self, trainer, pl_module):

pytorch_lightning/trainer/trainer.py

@@ -877,6 +877,9 @@ def default_root_dir(self) -> str:
         The default location to save artifacts of loggers, checkpoints etc.
         It is used as a fallback if logger or checkpoint callback do not define specific save paths.
         """
+        if "://" in str(self._default_root_dir):
+            # it is a remote uri, use as is
+            return self._default_root_dir
         return os.path.normpath(self._default_root_dir)
 
     @property
@@ -885,6 +888,9 @@ def weights_save_path(self) -> str:
         The default root location to save weights (checkpoints), e.g., when the
         :class:`~pytorch_lightning.callbacks.model_checkpoint.ModelCheckpoint` does not define a file path.
         """
+        if "://" in str(self._weights_save_path):
+            # it is a remote uri, use as is
+            return self._weights_save_path
         return os.path.normpath(self._weights_save_path)
 
     # -----------------------------

pytorch_lightning/utilities/cloud_io.py

@@ -1,4 +1,4 @@
-import sys
+import platform
 import os
 from typing import Union
 from pathlib import Path
@@ -35,14 +35,15 @@ def modern_gfile():
     file operations
     """
     tb_version = version.parse(tensorboard.version.VERSION)
-    modern_gfile = tb_version >= version.parse('2.0')
+    modern_gfile = tb_version >= version.parse("2.0")
+    return modern_gfile
 
 
-def cloud_open(path: pathlike, mode: str, newline:str = None):
-    if sys.platform == "win32":
+def cloud_open(path: pathlike, mode: str, newline: str = None):
+    if platform.system() == "Windows":
         log.debug(
             "gfile does not handle newlines correctly on windows so remote files are not"
-            "supported falling back to normal local file open."
+            " supported falling back to normal local file open."
         )
         return open(path, mode, newline=newline)
     if not modern_gfile():