Revert "Handle BaseExceptions (pallets#2222)"

This reverts commit 1d4448a.

CHANGES

@@ -14,9 +14,6 @@ Major release, unreleased
 - Change default configuration `JSONIFY_PRETTYPRINT_REGULAR=False`. jsonify()
   method returns compressed response by default, and pretty response in
   debug mode.
-- Call `ctx.auto_pop` with the exception object instead of `None`, in the
-  event that a `BaseException` such as `KeyboardInterrupt` is raised in a
-  request handler.
 
 Version 0.12.1
 --------------

flask/app.py

@@ -1991,9 +1991,6 @@ def wsgi_app(self, environ, start_response):
             except Exception as e:
                 error = e
                 response = self.handle_exception(e)
-            except:
-                error = sys.exc_info()[1]
-                raise
             return response(environ, start_response)
         finally:
             if self.should_ignore_error(error):

tests/test_basic.py

@@ -791,23 +791,6 @@ def after_request(resp):
         assert resp.data == b'internal server error'
 
 
-def test_baseexception_error_handling():
-    app = flask.Flask(__name__)
-    app.config['LOGGER_HANDLER_POLICY'] = 'never'
-
-    @app.route('/')
-    def broken_func():
-        raise KeyboardInterrupt()
-
-    with app.test_client() as c:
-        with pytest.raises(KeyboardInterrupt):
-            c.get('/')
-
-        ctx = flask._request_ctx_stack.top
-        assert ctx.preserved
-        assert type(ctx._preserved_exc) is KeyboardInterrupt
-
-
 def test_before_request_and_routing_errors():
     app = flask.Flask(__name__)