Fix pylint: do not use bare 'except' (#5025)

* Fix E722, do not use bare 'except'

* Remove used codes

* Add FileNotFoundError in LoadImagesAndLabels

* Remove AssertionError

* Ignore LoadImagesAndLabels

* Ignore downloads.py

* Ignore torch_utils.py

* Ignore train.py

* Ignore datasets.py

* Enable utils/download.py

* Fixing exception in thop

* Remove unused code

* Fixing exception in LoadImagesAndLabels

* Fixing exception in exif_size

* Fixing exception in parse_model

* Ignore exceptions in requests

* Revert the exception as suggested

* Revert the exception as suggested

models/tf.py

@@ -268,7 +268,7 @@ def parse_model(d, ch, model, imgsz):  # model_dict, input_channels(3)
         for j, a in enumerate(args):
             try:
                 args[j] = eval(a) if isinstance(a, str) else a  # eval strings
-            except:
+            except NameError:
                 pass
 
         n = max(round(n * gd), 1) if n > 1 else n  # depth gain