Bugfix/rework: IPv6 scope errors

[isbm]

What does this PR do?

• Fixes IPv6 scope issues that aren't supported in Python ipaddress.
• Support IPv6 scope at IPv6Address object level.
• Reworks salt._compat for code duplication and other issues
• Fixes import of ipaddress across everywhere
• Uses proper ipaddress instance for Python 3
• Adds debug logging instead of just pass.

What issues does this PR fix or reference?

Previous Behavior

If your /etc/resolv.conf has a scope in IPv6 address, something like this:

nameserver fe80::20d:b9ff:fe01:ea8%eth0

...then you are getting errors like this:

  2018-09-15 13:14:45,014 [salt.utils.dns   :1039][ERROR   ][845] 
  /etc/resolv.conf: u'fe80::20d:b9ff:fe01:ea8%eth0' does not
  appear to be an IPv4 or IPv6 address

This is hitting users since 2016: #37949

New Behavior

🤘 😎 🤘

Tests written?

Existing should just pass.

[meaksh]

Looks good 👍

[rallytime]

Hi @isbm! 😄

There are some test failures that are related to this change:

• integration.ssh.test_jinja_filters.SSHJinjaFiltersTest.test_network_ipaddr
• unit.utils.test_jinja.TestCustomExtensions.test_ipaddr
• unit.utils.test_jinja.TestCustomExtensions.test_ipv4
• unit.utils.test_jinja.TestCustomExtensions.test_ipv6
• unit.utils.test_jinja.TestCustomExtensions.test_is_ip
• unit.utils.test_jinja.TestCustomExtensions.test_is_ipv4
• unit.utils.test_jinja.TestCustomExtensions.test_is_ipv6

Can you take another look? 😎

https://jenkinsci.saltstack.com/job/pr-kitchen-centos7-py3/job/PR-49705/9/

[aphor]

FWIW, upstream in Python we have precedent to suggest upstream fixes in ipaddress module.

• https://bugs.python.org/issue23448
• https://bugs.python.org/issue29375

so I submitted https://bugs.python.org/issue34788

[isbm]

@aphor this doesn't really help, I've been there already. First, the issue is like three years old. Second, even they will fix in some upcoming versions, we still need this even on 2.7 and SUSE on 2.6 that is just simply EOL. Alas, if they finally get it done one day, we can incorporate that where it is needed. Will they fix it across everywhere? I doubt it.

But having Salt crashing on scoped IPv6 today is simply a no go.

[aphor]

@isbm I agree completely salt should not wait for upstream fix, but this is technical debt which would ideally be factored out of salt, and FWIW, salt isn't the only Python utility that I need to support IPv6.

I put that stuff here, mostly because it will be useful in the future to have it here, for reference, not to imply we should not merge this PR into salt.

[isbm]

@aphor after @rallytime puts that in (I am also going to backport that to 2018.3) let's look again at your PR. I am keeping an eye on yours and if you need any help, please ping me.

[avolmensky]

I have been playing around with 2019.02 and the netbox pillar module is broken with Python 3. The changes in this PR fix the problem I have been having. Will this be merged into the 2019.02 release?