Drop support for EOL Python 2.6, 3.2 and 3.3

[hugovk]

Summary: pathspec used to support Python 2.6 because it's a dependency of yamllint, which in turn is a dependency Ansible, which supported Python 2.6. Ansible has now dropped 2.6, so yamllint and pathspec may also drop it.

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Python 2.6, 3.2 and 3.3 are EOL and no longer receiving security updates (or any updates) from the core Python team.

Version	Release date	Supported until
2.6	2008-10-01	2013-10-29
3.2	2011-02-20	2016-02-27
3.3	2012-09-29	2017-09-29

Source: https://en.wikipedia.org/wiki/CPython#Version_history

They're also little used. Here's the pip installs for pathspec from PyPI for last month:

category	percent	downloads
2.7	56.50%	372,224
3.6	29.41%	193,745
3.5	7.67%	50,527
3.7	2.58%	17,008
3.4	2.49%	16,390
null	1.29%	8,500
3.3	0.04%	233
2.6	0.03%	208
3.2	0.00%	3
3.8	0.00%	3
Total		658,841

Source: pypistats python_minor --last-month pathspec

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Ansible 2.7.0 was released in October 2018 which drops Python 2.6.

• https://deleforterie.com/wordpress/index.php/2018/10/21/ansible-python-2-6-support-ends-with-ansible-2-7/
• https://github.com/ansible/ansible/releases/tag/v2.7.0
• Exorcise Python-2.6 ansible/ansible#42971

• Support for running an Ansible controller with Python-2.6 has been dropped. You can still manage machines which use Python-2.6 but you will have to manage them from a machine which has Python-2.7 or Python-3.5 or greater installed. See the porting guide if you need more information.

https://github.com/ansible/ansible/blob/stable-2.7/changelogs/CHANGELOG-v2.7.rst#v2-7-0

The decision to drop Python-2.6 support on the controller was made because many dependent libraries are becoming unavailable there. In particular, python-cryptography is no longer available for Python-2.6 and the last release of pycrypto (the alternative to python-cryptography) has known security bugs which will never be fixed.

https://docs.ansible.com/ansible/latest/porting_guides/porting_guide_2.7.html#python-compatibility

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This PR:

• Includes PR Test on Travis CI #23 to test on Travis CI
• Drops support for EOL Python versions
• Upgrade Python syntax with pyupgrade
• Add python_requires to help pip

[cpburnz]

Since yamllint has dropped support for Python 2.6, 3.2 and 3.3 I'll happily drop support for them because that was the reason I supported them. Thank you for finding this and for the stats.

[hugovk]

You're welcome!