Prevent allow_unsafe_werkzeug option from being passed to web servers (…

…Fixes #2001)

src/flask_socketio/__init__.py

@@ -627,15 +627,14 @@ def run(self, app, host=None, port=None, **kwargs):  # pragma: no cover
             self.sockio_mw.wsgi_app = DebuggedApplication(
                 self.sockio_mw.wsgi_app, evalex=True)
 
+        allow_unsafe_werkzeug = kwargs.pop('allow_unsafe_werkzeug', False)
         if self.server.eio.async_mode == 'threading':
             try:
                 import simple_websocket  # noqa: F401
             except ImportError:
                 from werkzeug._internal import _log
                 _log('warning', 'WebSocket transport not available. Install '
                                 'simple-websocket for improved performance.')
-            allow_unsafe_werkzeug = kwargs.pop('allow_unsafe_werkzeug',
-                                               False)
             if not sys.stdin or not sys.stdin.isatty():  # pragma: no cover
                 if not allow_unsafe_werkzeug:
                     raise RuntimeError('The Werkzeug web server is not '