temporary mitigation of bug 551604

packages/api-utils/lib/loader.js

@@ -163,8 +163,14 @@ const evaluate = iced(function evaluate(sandbox, uri, options) {
     source: null
   }, options);
 
-  return source ? Cu.evalInSandbox(source, sandbox, version, uri, line)
-                : loadSubScript(uri, sandbox, encoding);
+  try {
+    return source ? Cu.evalInSandbox(source, sandbox, version, uri, line)
+                  : loadSubScript(uri, sandbox, encoding);
+  } catch (exc if exc.name === "SyntaxError") {
+    // see https://bugzilla.mozilla.org/show_bug.cgi?id=551604
+    throw SyntaxError(exc.message+' at '+exc.fileName+':'+exc.lineNumber,
+                      exc.fileName, exc.lineNumber);
+  }
 });
 exports.evaluate = evaluate;