Fix issue wit custom authorizers when using pseudo parameters plugin

lib/stackops/apiGateway.js

@@ -221,17 +221,16 @@ module.exports = function(currentTemplate, aliasStackTemplates, currentAliasStac
 		});
 
 		// Audjust authorizer Uri and name (stage variables are not allowed in Uris here)
+		const isExternalRefAuthorizerPredicate = part => _.startsWith(part, 'arn:aws:lambda') ||
+			(_.has(part, 'Fn::Sub') && _.startsWith(part['Fn::Sub'], 'arn:aws:lambda'))
 		_.forOwn(authorizers, (authorizer, name) => {
 			const authorizerType = _.get(authorizer, 'Properties.Type');
 			if (authorizerType === 'TOKEN' || authorizerType === 'REQUEST') {
 				const uriParts = authorizer.Properties.AuthorizerUri['Fn::Join'][1];
-				const isExternalRefAuthorizer = _.every(uriParts, part => !_.startsWith(part, 'arn:aws:lambda'));
-				if (isExternalRefAuthorizer) {
-					const funcIndex = _.findIndex(uriParts, part => 
-						_.has(part, 'Fn::GetAtt') || _.startsWith(part, 'arn:aws:lambda'));
-
-					// Use the SERVERLESS_ALIAS stage variable to determine the called function alias
-					uriParts.splice(funcIndex + 1, 0, ':${stageVariables.SERVERLESS_ALIAS}');
+				const isExternalRefAuthorizer = _.some(uriParts, isExternalRefAuthorizerPredicate);
+				if (!isExternalRefAuthorizer) {
+					const funcIndex = _.findIndex(uriParts, part => _.startsWith('/invocations'));
+					uriParts.splice(funcIndex , 0, ':${stageVariables.SERVERLESS_ALIAS}');
 				}
 			}
 
@@ -269,7 +268,7 @@ module.exports = function(currentTemplate, aliasStackTemplates, currentAliasStac
 			const functionName = _.replace(name, /LambdaPermissionApiGateway$/, '');
 			const versionName = _.find(_.keys(versions), version => _.startsWith(version, functionName));
 			const aliasName = _.find(_.keys(aliases), alias => _.startsWith(alias, functionName));
-			const isExternalRef = _.startsWith(permission.Properties.FunctionName, 'arn:aws:lambda'); 
+			const isExternalRef = isExternalRefAuthorizerPredicate(permission.Properties.FunctionName); 
 
 			// Adjust references and alias permissions
 			if (!isExternalRef) {