Remove Python 2 compatibility and use of six module #177

Job	Run time
Build wxPython documentation	0s
build-source-dist	8m 36s
build-wheels (ubuntu-22.04, 3.9, x64)	24m 29s
build-wheels (ubuntu-22.04, 3.13, x64)	23m 30s
build-wheels (windows-2022, 3.9, x86)	24m 52s
build-wheels (windows-2022, 3.9, x64)	22m 43s
build-wheels (windows-2022, 3.13, x86)	24m 43s
build-wheels (windows-2022, 3.13, x64)	23m 50s
build-wheels (macos-13, 3.9, x64)	43m 46s
build-wheels (macos-13, 3.13, x64)	31m 32s
Upload wheels to snapshot-builds on wxpython.org	0s
Publish Python distribution to PyPI	0s
Create GitHub Release and upload source	0s
	3h 48m 1s

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