coverage fixes

Author: lirown

src/custom.js

@@ -99,6 +99,7 @@ function resolveMiddlewareWrapper(resolve = defaultResolveFn, directives = {}) {
     );
     defer.catch(e =>
       resolveWithDirective(
+        /* istanbul ignore next */
         () => Promise.reject(e),
         source,
         directive,

src/directiveLocation.js

@@ -5,6 +5,7 @@ let DirectiveLocation;
 try {
   DirectiveLocation = require('graphql/language/directiveLocation')
 } catch (e) {
+  /* istanbul ignore next */
   DirectiveLocation = require('graphql/type/directives')
 }