usability: message for no resources found

[kmova]

When the cluster doesn't have required resources, display a helpful message instead of displaying nothing.

In my cluster that doesn't have any pools setup at, I get the following:

kiran_mova_mayadata_io@kmova-dev:~$ kubectl openebs get storage
kiran_mova_mayadata_io@kmova-dev:~$ 

It would nice to display a message like this:

kiran_mova_mayadata_io@kmova-dev:~$ kubectl get cspc
No resources found in default namespace.

Also, while at this - check the message displayed when there is no openebs installed in the cluster.

[vharsh]

Okay starting notes on implementation:

• For the volume & storage sub-commands, the code can run a single function(when cas-type is given in via flags) or run all functions when no cas-type flags are given.
• The code under interest is, pkg/storage/storage.go, pkg/volume/volume.go, pkg/persistentvolumeclaim/persistentvolumeclaim.go & pkg/blockdevice/blockdevice.go
• If a single function is executed(i.e. cas-type is supplied), a standard message & a standard error can be thrown by that cas-implementer function
• When cas-type isn't supplied, the errors might be stored in a slice & shown accordingly(a volume is a PersistentVolume, but a storage can be a two or three different kinds of resources, so having all errors would help)

For more help, do join the OpenEBS-Dev slack.

[Abhishek-kumar09]

Working on it.