Check kernel id before delete and upgrade ws (#1376)

Co-authored-by: saf <[email protected]>

Author: vegetablest

enterprise_gateway/services/kernels/handlers.py

@@ -146,6 +146,24 @@ def get(self, kernel_id: str):
         model = km.kernel_model(kernel_id)
         self.finish(json.dumps(model, default=date_default))
 
+    @web.authenticated
+    async def delete(self, kernel_id):
+        """Remove a kernel."""
+        self.kernel_manager.check_kernel_id(kernel_id=kernel_id)
+        await super().delete(kernel_id=kernel_id)
+
+
+class ZMQChannelsHandler(
+    TokenAuthorizationMixin, CORSMixin, JSONErrorsMixin, jupyter_server_handlers.ZMQChannelsHandler
+):
+    """Extends the kernel websocket handler."""
+
+    async def get(self, kernel_id):
+        """Handle a get request for a kernel."""
+        # Synchronize Kernel and check if it exists.
+        self.kernel_manager.check_kernel_id(kernel_id=kernel_id)
+        await super().get(kernel_id=kernel_id)
+
 
 default_handlers: list[tuple] = []
 for path, cls in jupyter_server_handlers.default_handlers: