testing/py3-wxpython: Fixed file permissions

Some of the installed python files are installed with permissions 600, so that
(non-root) users cannot load the module properly. The fix was is almost copied
in verbatim from Arch Linux.
7 jobs for !717 with py3-wxpython in 24 minutes and 8 seconds (queued for 3 seconds)
detached
Status Job ID Name Coverage
  Lint
passed #7571
docker-alpine x86_64
lint

00:00:30

 
  Build
passed #7576
docker-alpine ci-build aarch64
build-aarch64

00:04:57

passed #7577
docker-alpine ci-build armv7
build-armv7

00:04:04

passed #7575
docker-alpine ci-build ppc64le
build-ppc64le

00:04:11

passed #7574
docker-alpine ci-build s390x
build-s390x

00:10:00

passed #7573
docker-alpine ci-build x86
build-x86

00:13:27

passed #7572
docker-alpine ci-build x86_64
build-x86_64

00:02:56