Install work in python3.8

[SabatierBoris]

platform.linux_distribution is removed in python 3.8 a we should use distro package instead.

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[msftclas]

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[haroldrandom]

1. Don't need to add dependency requirement and update *.py3.*.txt and setup.py?
2. According to https://pypi.org/project/distro/ , "Distro currently supports Linux and BSD based systems but Windows and OS X support is also planned." What about Windows platform?

[haroldrandom]

Hey, @SabatierBoris Thanks for you contribution!

We have received a lot issues about that installation problem. And sincerely considered your suggestion. distro is a really good alternative of platform.dist() and platform.linux_distribution(). And it's recommended by Python Offical Documentation.

However, the installation script is a bit irrational, done many things and its code is not so clean. We may refine that script in the future.
Also, considering we only need a small part of the functionality. we descided not to introduce distro into azure-cli. We fix that by a small simple alternative function, PR #11322.

But It's also possible that we will bring in distro in some days.

We did get inspired by your idea. Appreciated that.