W&B: DDP fix (#5176)

utils/loggers/wandb/wandb_utils.py

@@ -19,6 +19,13 @@ from utils.datasets import LoadImagesAndLabels
 from utils.datasets import img2label_paths
 from utils.general import check_dataset, check_file
 
+try:
+    import wandb
+
+    assert hasattr(wandb, '__version__')  # verify package import not local dir
+except (ImportError, AssertionError):
+    wandb = None
+    
 RANK = int(os.getenv('RANK', -1))
 WANDB_ARTIFACT_PREFIX = 'wandb-artifact://'