Pyflakes fix for builtin modules (python3)

[ghost]

Hi, I let pyflakes for python3 take a look a the Builtin modules (result below). I've addressed those issues within this PR. It should also make the Builtin modules Python 3 compatible, I don't see how these changes could affect the working of LUI with Python2.

Builtin/Elements.py:13: 'from panda3d.lui import *' used; unable to
detect undefined names
Builtin/Elements.py:14: 'panda3d.core.Point2' imported but unused
Builtin/Elements.py:16: 'functools.partial' imported but unused
Builtin/Elements.py:17: 'from LUILayouts import *' used; unable to
detect undefined names
Builtin/Elements.py:19: 'math' imported but unused
Builtin/Elements.py:27: 'LUIObject' may be undefined, or defined from
star imports: LUILayouts, panda3d.lui
Builtin/Elements.py:30: 'LUIObject' may be undefined, or defined from
star imports: LUILayouts, panda3d.lui
Builtin/Elements.py:42: 'LUISlider' may be undefined, or defined from
star imports: LUILayouts, panda3d.lui
Builtin/Elements.py:66: 'LUIObject' may be undefined, or defined from
star imports: LUILayouts, panda3d.lui
Builtin/Elements.py:69: 'LUIObject' may be undefined, or defined from
star imports: LUILayouts, panda3d.lui
Builtin/Elements.py:70: 'LUISprite' may be undefined, or defined from
star imports: LUILayouts, panda3d.lui
Builtin/Elements.py:71: 'LUISprite' may be undefined, or defined from
star imports: LUILayouts, panda3d.lui
Builtin/Elements.py:72: 'LUISprite' may be undefined, or defined from
star imports: LUILayouts, panda3d.lui
Builtin/Elements.py:95: 'LUIObject' may be undefined, or defined from
star imports: LUILayouts, panda3d.lui
Builtin/Elements.py:98: 'LUIObject' may be undefined, or defined from
star imports: LUILayouts, panda3d.lui
Builtin/Elements.py:111: 'LUIObject' may be undefined, or defined from
star imports: LUILayouts, panda3d.lui
Builtin/Elements.py:114: 'LUIObject' may be undefined, or defined from
star imports: LUILayouts, panda3d.lui
Builtin/Elements.py:116: 'LUISprite' may be undefined, or defined from
star imports: LUILayouts, panda3d.lui
Builtin/Elements.py:118: 'LUISprite' may be undefined, or defined from
star imports: LUILayouts, panda3d.lui
Builtin/Elements.py:124: 'LUISprite' may be undefined, or defined from
star imports: LUILayouts, panda3d.lui
Builtin/Elements.py:220: 'LUIObject' may be undefined, or defined from
star imports: LUILayouts, panda3d.lui
Builtin/Elements.py:222: 'LUISprite' may be undefined, or defined from
star imports: LUILayouts, panda3d.lui
Builtin/Elements.py:225: 'LUISprite' may be undefined, or defined from
star imports: LUILayouts, panda3d.lui
Builtin/Elements.py:231: 'LUISprite' may be undefined, or defined from
star imports: LUILayouts, panda3d.lui
Builtin/Elements.py:237: 'LUIObject' may be undefined, or defined from
star imports: LUILayouts, panda3d.lui
Builtin/Elements.py:238: 'LUISprite' may be undefined, or defined from
star imports: LUILayouts, panda3d.lui
Builtin/Elements.py:240: 'LUISprite' may be undefined, or defined from
star imports: LUILayouts, panda3d.lui
Builtin/Elements.py:248: 'LUIVerticalLayout' may be undefined, or
defined from star imports: LUILayouts, panda3d.lui
Builtin/Elements.py:263: 'LUIObject' may be undefined, or defined from
star imports: LUILayouts, panda3d.lui
Builtin/Elements.py:264: 'LUISprite' may be undefined, or defined from
star imports: LUILayouts, panda3d.lui
Builtin/Elements.py:265: 'LUISprite' may be undefined, or defined from
star imports: LUILayouts, panda3d.lui
Builtin/Elements.py:321: 'unicode' may be undefined, or defined from
star imports: LUILayouts, panda3d.lui
Builtin/Elements.py:322: 'unicode' may be undefined, or defined from
star imports: LUILayouts, panda3d.lui
Builtin/Elements.py:323: 'unicode' may be undefined, or defined from
star imports: LUILayouts, panda3d.lui
Builtin/LUIProgressbar.py:72: undefined name 'unicode'
Builtin/LUISpriteButton.py:4: 'LUILabel.LUILabel' imported but unused
Builtin/LUISpriteButton.py:15: undefined name 'width'
Builtin/LUISpriteButton.py:16: undefined name 'height'
Builtin/LUIScrollableRegion.py:55: local variable 'scroll_shadow_width'
is assigned to but never used
Builtin/LUILayouts.py:7: 'direct.directnotify.DirectNotify.DirectNotify'
imported but unused
Builtin/LUILabel.py:23: undefined name 'unicode'
Builtin/LUILabel.py:41: undefined name 'unicode'
Builtin/LUILabel.py:63: undefined name 'unicode'
Builtin/LUILabel.py:65: undefined name 'unicode'
Builtin/LUISelectbox.py:196: undefined name 'unicode'
Builtin/LUIInputField.py:80: undefined name 'unicode'

[tobspr]

Awesome, thanks a lot!