hermes config validate reports success when no config

[plafer]

Summary of Bug

When no config file is present at ~/.hermes/config.toml, hermes config validate prints the following errors, and then indicates success.

% hermes config validate
2022-04-26T14:26:37.372557Z ERROR ThreadId(01) could not find configuration file at '/Users/plafer/.hermes/config.toml'
2022-04-26T14:26:37.372605Z ERROR ThreadId(01) for an example, please see https://hermes.informal.systems/config.html#example-configuration-file
Success: "configuration is valid"

Version

v0.13

Steps to Reproduce

1. ensure no file is present at ~/.hermes/config.toml
2. Run hermes config validate
3. Notice that the command succeeds

Acceptance Criteria

hermes config validate does not succeed when no config file is present.

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[plafer]

Additionally, if there is an empty file, the command reports success as well. IIUC, this should fail as not all required fields are present.