normalize pathnames to fix issue 1830 (#1831)

Thank you @algat! And thanks @mthrok for the review!

Author: algat

intermediate_source/speech_command_classification_with_torchaudio_tutorial.py

@@ -79,7 +79,7 @@ def __init__(self, subset: str = None):
         def load_list(filename):
             filepath = os.path.join(self._path, filename)
             with open(filepath) as fileobj:
-                return [os.path.join(self._path, line.strip()) for line in fileobj]
+                return [os.path.normpath(os.path.join(self._path, line.strip())) for line in fileobj]
 
         if subset == "validation":
             self._walker = load_list("validation_list.txt")