Forward richer errors on GKE cluster creation failure

Problem to solve

When cluster creation fails, we only say

Failed to request to CloudPlatform; Invalid request

which is not very informative. This is typically a user error, but the user is left to guess the cause.

Proposal

The error classes also have header, body and status_code, which may hold useful information.

Edited by Hordur Freyr Yngvason