How to make button text bold in Tkinter?

[scratchmyhead]

I've googled this but can't find an answer. I just want to make the text on a button bold.

[menator01]

import tkinter as tk

root = tk.Tk()

button = tk.Button(None, text='Button', font='sans 16 bold').pack()

root.mainloop()

[scratchmyhead]

Thank you