Skip tests if they cannot be run

If configured with `mvt.usePostGIS` but with no postgis version
supporting it, they should be skipped.

test/acceptance/date-wrapping.spec.js

@@ -2,8 +2,13 @@
 const assert = require('assert');
 const TestClient = require('../support/test-client');
 const mapConfigFactory = require('../fixtures/test_mapconfigFactory');
+const serverOptions = require('../../lib/cartodb/server_options');
 
-describe('date-wrapping', () => {
+const usePgMvtRenderer = serverOptions.renderer.mvt.usePostGIS;
+const postgisVersion = process.env.POSTGIS_VERSION;
+const describe_mvt = postgisVersion >= '20400' || !usePgMvtRenderer ? describe : describe.skip;
+
+describe_mvt('date-wrapping', () => {
     let testClient;
 
     describe('when a map instantiation has one single layer', () => {