[#61] Show error in inexistent routes
closes #61 (closed)
The error will be shown in the following cases:
- https://notifications.web.cern.ch/thispathdoesntexist
- https://notifications.web.cern.ch/channels/3ede6edf-7565-4308-b79b-c73e5859641f/channelexistsbutnotthispath
