Error log for 'avocado image'

[smitterl]

Is your feature request related to a problem? Please describe.

One of my test executions fails with Provider not available and the test can't execute.
When I manually execute avocado vmimage get... I just get the info The requested image could not be downloaded but no way to know why it failed.

Describe the solution you'd like

Avocado should log the error

1. On journald
2. Via --verbose or --debug flag

Describe alternatives you've considered
A clear and concise description of any alternative solutions or features you've considered.

Additional information
Add any additional information or screenshots about the feature request here.