Directing to an internal site from graph callback

i have graph with some data points. when the use selects a data point, i have to direct them to the source of the data point. But, when the data point is not available i have to redirect them to an internal site saying that the data point no longer exists.

when the data is available i am using webbrowser.open_new_tab(url) to open the source of the data point in the new tab when it is not available i cant do the same because url generated is a relative link and chrome cant open that.

Appreciate any help.