include mapbox.style value that start by mapbox://

... in list that require mapbox access token

src/plots/mapbox/index.js

@@ -270,7 +270,10 @@ function findAccessToken(gd, mapboxIds) {
 }
 
 function isMapboxStyle(s) {
-    return typeof s === 'string' && constants.styleValuesMapbox.indexOf(s) !== -1;
+    return typeof s === 'string' && (
+        constants.styleValuesMapbox.indexOf(s) !== -1 ||
+        s.indexOf('mapbox://') === 0
+    );
 }
 
 exports.updateFx = function(gd) {

test/jasmine/tests/mapbox_test.js

@@ -399,6 +399,27 @@ describe('mapbox credentials', function() {
         });
     }, LONG_TIMEOUT_INTERVAL);
 
+    it('@gl should not throw when using a custom mapbox style URL with an access token in the layout', function(done) {
+        var cnt = 0;
+
+        Plotly.plot(gd, [{
+            type: 'scattermapbox',
+            lon: [10, 20, 30],
+            lat: [10, 20, 30]
+        }], {
+            mapbox: {
+                accesstoken: MAPBOX_ACCESS_TOKEN,
+                style: 'mapbox://styles/etpinard/cip93fm98000sbmnuednknloo'
+            }
+        }).catch(function() {
+            cnt++;
+        }).then(function() {
+            expect(cnt).toEqual(0);
+            expect(gd._fullLayout.mapbox.accesstoken).toBe(MAPBOX_ACCESS_TOKEN);
+            done();
+        });
+    }, LONG_TIMEOUT_INTERVAL);
+
     it('@gl should log when an access token is set while using a custom non-mapbox style', function(done) {
         spyOn(Lib, 'log');
         var cnt = 0;