Improve error reporting to api consumers

[sondove]

The novem service, whilst imperfect, does try to provide meaningful error messages to the customer. The novem python library should be more aware of these error messages and provide it to the customer in a natural way.

• For non critical errors we should ignore them (this will be available in the log)
• For critical errors we should throw an exception in the case of python and print to stderr with a non-zero return value in the case of the cli

[sondove]

For example for connectivity errors we could do better than this default stack trace