Understand new filterErrorStack config option

When this option is true, error stack lines relating to
'internal/process' and 'node_modules' modules will be filtered out.

In the future, this option may also allow a regex, similar to
excludeInstrumentation.

lib/util.js

@@ -4,6 +4,7 @@ define([
 	'dojo/lang',
 	'dojo/Promise',
 	'./EnvironmentType',
+	'../main',
 	'diff',
 	'dojo/has!host-node?dojo/node!glob',
 	'dojo/has!host-node?dojo/node!path',
@@ -16,6 +17,7 @@ define([
 	lang,
 	Promise,
 	EnvironmentType,
+	intern,
 	diffUtil,
 	glob,
 	pathUtil,
@@ -466,7 +468,7 @@ define([
 	/**
 	 * Parse a stack trace, apply any source mappings, and normalize its format.
 	 */
-	function normalizeStackTrace(stack) {
+	function normalizeStackTrace(stack, filterStack) {
 		var lines = stack.replace(/\s+$/, '').split('\n');
 		var firstLine = '';
 
@@ -482,6 +484,16 @@ define([
 		}
 
 		stack = /^\s*at /.test(lines[0]) ? processChromeTrace(lines) : processSafariTrace(lines);
+
+		if (filterStack) {
+			stack = stack.filter(function (line) {
+				return !(
+					/internal\/process\//.test(line) ||
+					/node_modules\//.test(line)
+				);
+			});
+		}
+
 		return '\n' + firstLine + stack.join('\n');
 	}
 
@@ -633,7 +645,8 @@ define([
 						stack = stack.slice(String(error.message).length);
 					}
 
-					stack = normalizeStackTrace(stack);
+					var filterStack = intern && intern.config && intern.config.filterErrorStack;
+					stack = normalizeStackTrace(stack, filterStack);
 				}
 
 				if (error.showDiff && typeof error.actual === 'object' && typeof error.expected === 'object') {