more adjustments for lint

Author: BSd3v

dash/dash.py

@@ -449,18 +449,18 @@ def __init__(  # pylint: disable=too-many-statements
 
         if use_async is None:
             try:
-                import asgiref  # pylint: disable=unused-import # noqa
+                import asgiref  # pylint: disable=unused-import, import-outside-toplevel # noqa
 
                 use_async = True
             except ImportError:
                 pass
         elif use_async:
             try:
-                import asgiref  # pylint: disable=unused-import # noqa
-            except ImportError:
+                import asgiref  # pylint: disable=unused-import, import-outside-toplevel # noqa
+            except ImportError as exc:
                 raise Exception(
                     "You are trying to use dash[async] without having installed the requirements please install via: `pip install dash[async]`"
-                )
+                ) from exc
 
         _validate.check_obsolete(obsolete)