Fix TypeError: exceptions must derive from BaseException (#329)

* Fix TypeError: exceptions must derive from BaseException

* Fix WSGIAppError rewrapping

---------

Co-authored-by: Corentin ARNOULD <corentin@keepcalm.dev>

Author: Koalab99

gabbi/case.py

@@ -513,8 +513,8 @@ def _run_request(
             )
         except wsgi_intercept.WSGIAppError as exc:
             # Extract and re-raise the wrapped exception.
-            raise (exc.exception_type, exc.exception_value,
-                   exc.traceback)
+            raise exc.exception_type(exc.exception_value).with_traceback(
+                   exc.traceback) from None
 
         # Set headers and location attributes for follow on requests
         self.response = response