Place error messages on a single line and include filename

Error messages at the moment don't carry context, which makes finding
errors when testing multiple files hard. Error messages also
take up lots of space currently. This commit resolves those issues.

Author: garethr

kubeval/kubeval.go

@@ -110,13 +110,13 @@ func validateResource(data []byte, schemaCache map[string]*gojsonschema.Schema,
 
 	kind, err := getString(body, "kind")
 	if err != nil {
-		return result, err
+		return result, fmt.Errorf("Error with %s: %s", result.FileName, err.Error())
 	}
 	result.Kind = kind
 
 	apiVersion, err := getString(body, "apiVersion")
 	if err != nil {
-		return result, err
+		return result, fmt.Errorf("Error with %s: %s", result.FileName, err.Error())
 	}
 	result.APIVersion = apiVersion
 
@@ -126,7 +126,7 @@ func validateResource(data []byte, schemaCache map[string]*gojsonschema.Schema,
 
 	schemaErrors, err := validateAgainstSchema(body, &result, schemaCache, config)
 	if err != nil {
-		return result, err
+		return result, fmt.Errorf("Error with %s: %s", result.FileName, err.Error())
 	}
 	result.Errors = schemaErrors
 	return result, nil
@@ -178,6 +178,7 @@ func downloadSchema(resource *ValidationResult, schemaCache map[string]*gojsonsc
 	}
 
 	var errors *multierror.Error
+
 	for _, schemaRef := range schemaRefs {
 		schemaLoader := gojsonschema.NewReferenceLoader(schemaRef)
 		schema, err := gojsonschema.NewSchema(schemaLoader)
@@ -191,6 +192,10 @@ func downloadSchema(resource *ValidationResult, schemaCache map[string]*gojsonsc
 		errors = multierror.Append(errors, wrappedErr)
 	}
 
+    if errors != nil {
+	    errors.ErrorFormat = singleLineErrorFormat
+    }
+
 	// We couldn't find a schema for this resource. Cache it's lack of existence, then stop
 	schemaCache[resource.VersionKind()] = nil
 	return nil, errors.ErrorOrNil()
@@ -270,5 +275,17 @@ func ValidateWithCache(input []byte, schemaCache map[string]*gojsonschema.Schema
 			results = append(results, result)
 		}
 	}
+
+    if errors != nil {
+	    errors.ErrorFormat = singleLineErrorFormat
+    }
 	return results, errors.ErrorOrNil()
 }
+
+func singleLineErrorFormat(es []error) string {
+    messages := make([]string, len(es))
+    for i, e := range es {
+        messages[i] = e.Error()
+    }
+    return strings.Join(messages, "\n")
+}