Can't set Theme constants in gdscript.

[jtaart]

Godot version: Godot_v3.0-rc2_win64.exe
OS/device including version: win64

This no longer works:
get_theme().set_constant("separation", "HBoxContainer", 500)

Seems to work just fine in 2.1.4.

Might be related to #13071

[jtaart]

I got it to work. I still think it is some kind of bug though. If you leave the theme null in the editor. Then create a theme with theme.new(), and assign that theme to the node. It will not allow you to set the constants, but if you create the theme in the editor it will let you set the constants in gdscript. In 2.1.4 you can leave it null, then do everything in gdscript.