fix(conditions) prints validation error when found

[dduportal]

This PR is a fix for a bug I found while working on #289 .

It ensures that the validation error messages are printed to the end user when a condition failed to be validated.

Test

With a manifest having the following condition (missing spec.file)

# ...
conditions:
  checkUsername:
    kind: yaml
    spec:
      key: github.username

With updatecli 0.16.0, you got:

# ...
CONDITIONS:
===========

checkUsername
-------------
✗ condition not met, skipping pipeline

=> result is expected but no message to help the end user.

With this PR, you got:

$ go build -o ./dist/updatecli && ./dist/updatecli diff
# ...
CONDITIONS:
===========

checkUsername
-------------
ERROR: Validation error: the provided manifest configuration had the following validation errors:
Invalid spec for yaml resource: 'file' is empty.

✗ condition not met, skipping pipeline

=> which is clearly an improvement

Additional Information

Tradeoff

Potential improvement

[dduportal]

@olblak I've added this to the 0.16.1 as it's clearly worth a patch: sounds good for you?