Change QtGui to QtWidgets.

[carbonscott]

Made changes by the following command:

grep QtGui `find . -iname "*py"` | awk -F":" '{print $1}'  | uniq | xargs -I {} sed -i 's/QtGui/QtWidgets/g' {}
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# in-place change ___________________________________________________________________|

Though it is generally not recommended to do it like this, fortunately, it works fine after testing.