mbed dm init without API key gives out ugly backtrace, it would be better to handle the exception

[teetak01]

Currently if I run "mbed dm init ..." without any API-key defined, it gives quite long backtrace from cloud-sdk which can be confusing to understand.

It would be more clear to catch this Exception and point to either use "-a" flag to provide the API-key, or define CLOUD_SDK_API_KEY parameter.

[bridadan]

Hi @teetak01, I'm currently fixing this in an mbed-os PR: ARMmbed/mbed-os#9635

[ciarmcom]

Internal Jira reference: https://jira.arm.com/browse/MBOCUSTRIA-866

[cmonr]

@teetak01 Mind retesting with master? It just came in :)