Improve the error message of HTTP 404

[louischan-oursky]

Most likely the HTTP 404 is caused by incompatible versions between the client and the controller. We should print a message saying

The version of skycli may be incompatible with the cluster. Upgrade or downgrade the version of skycli may fix this problem.

[chpapa]

However, I think it is not really good if we show an uncertain error message for version error.

Do we have any versioning on our api now? By path or by headers (e.g Accept?)

If former case, I think we can assume if we call /v2.2/abc it return 404 just say "404 API version not found or endpoint not found"

If later case, we should be able to determine version not compatible by adding some details in API response

(Or we don't have api versioning at all?)

[louischan-oursky]

Do we have any versioning on our api now? By path or by headers (e.g Accept?)

Yes. In path.

The original problem is that the controller is too old that it does not have api versioning but the skycli has. Actually it is not a problem we will see in the wild because the controller should always be latest.