igluctl: Raise errors in parseable errorformat

[mrchief]

Igluctl lint reports errors that are spread over multiple lines and look something like this

Cannot read [com.test]: no valid JSON SchemasCannot parse [com.test/test_schema/jsonschema/1-0-0]: Unexpected character ('}' (code 125)): was expecting double-quote to start field name
 at [Source: {
  "$schema": "http://iglucentral.com/schemas/com.snowplowanalytics.self-desc/schema/jsonschema/1-0-0#",
  "description": "Test.",
  "self": {
    "vendor": "com.test",
    "name": "test_schema",
    "format": "jsonschema",
    "version": "1-0-0"
  },
  "type": "object",
  "properties": {

    "prop": {
      "description": "Test prop",
      "enum": ["test"]
    },

  },
  "minProperties": 1,
  "required": [
    "prop"
  ],
  "additionalProperties": false
}
; line: 18, column: 4]

It'd be great if the error could be formatted in {file}:{line}:{column}: {message} format. I'm building a lint action to validate and report errors on Github Pull Requests. Having errors output in this format opens up numerous possibilities like annotations and file suggestions.