Check scene paths, minor fix in pointnav generator (#111)

* check scene paths, minor fix in pointnav generator

habitat/datasets/pointnav/pointnav_dataset.py

@@ -35,7 +35,7 @@ class PointNavDatasetV1(Dataset):
     def check_config_paths_exist(config: Config) -> bool:
         return os.path.exists(
             config.POINTNAVV1.DATA_PATH.format(split=config.SPLIT)
-        )
+        ) and os.path.exists(config.SCENES_DIR)
 
     @staticmethod
     def get_scenes_to_load(config: Config) -> List[str]:

test/test_pointnav_dataset.py

@@ -141,6 +141,8 @@ def test_pointnav_episode_generator():
     config.DATASET.SPLIT = "val"
     config.ENVIRONMENT.MAX_EPISODE_STEPS = 500
     config.freeze()
+    if not PointNavDatasetV1.check_config_paths_exist(config.DATASET):
+        pytest.skip("Test skipped as dataset files are missing.")
     env = habitat.Env(config)
     env.seed(config.SEED)
     random.seed(config.SEED)