Skaffold should provide more detail on parsing errors

[briandealwis]

Invoking Skaffold with a skaffold.yaml produces a terse error message with no detail as the problem.

parsing skaffold config: error parsing skaffold configuration file

But skaffold fix will pinpoint the problematic line:

unable to parse config: yaml: unmarshal errors:
  line 4: field pimage not found in type latest.Artifact

We should report the problematic line.

[kschaab]

I think the priority is incorrect on this as this error is also returned from skaffold diagnose as well. Considering this:

  # Search for configuration issues and print the effective configuration
  skaffold diagnose

it seems like configuration issues like these should be more detailed than:

skaffold diagnose --yaml-only --filename skaffold.yaml
WARN[0000] Your Skaffold version might be too old. Download the latest version (1.24.0) from:
  https://github.com/GoogleContainerTools/skaffold/releases/tag/v1.24.0
parsing skaffold config: error parsing skaffold configuration file

[briandealwis]

Oops, This was fixed in #5722 for Skaffold 1.23.0:

$ skaffold diagnose --yaml-only
WARN[0000] Your Skaffold version might be too old. Download the latest version (1.24.0) from:
  https://github.com/GoogleContainerTools/skaffold/releases/tag/v1.24.0 
parsing skaffold config: error parsing skaffold configuration file: parsing api version: yaml: line 4: could not find expected ':'