Better error message when appliance_url doesn't match machine address in .netrc or conjur.identity

[whip113]

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

When summon-conjur is invoked and the address in appliance_url of the conjur.conf file doesn't match the address in machine of the conjur.identity file, summon-conjur exits with a generic error about failing to create a Conjur client.

Describe the solution you would like

When a conjur.identity file is found, but no credential is found in it (appliance_url does not match machine), summon-conjur should show a more helpful error like Conjur.identity file was read, but credential for machine https://server.name.com was not found. This would help with troubleshooting efforts.

Describe alternatives you have considered

Alternatively, this could be part of the verbose logging facility, though a simple config mistake like this should be more readily obtained IMO.