Add pip>=20.2 support

[atugushev]

Addressed breaking changes:

• Implement PEP 376 REQUESTED pypa/pip#8026

pip-20.2 release tracking issue: pypa/pip#8511

Changelog-friendly one-liner: Add pip>=20.2 support.

Contributor checklist

• Provided the tests for the changes.
• Gave a clear one-line description in the PR (that the maintainers can add to CHANGELOG.md on release).
• Assign the PR to an existing or new milestone for the target version (following Semantic Versioning).

[codecov]

Codecov Report

Merging #1168 into master will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master    #1168   +/-   ##
=======================================
  Coverage   99.51%   99.51%           
=======================================
  Files          36       36           
  Lines        2860     2862    +2     
  Branches      335      336    +1     
=======================================
+ Hits         2846     2848    +2     
  Misses          8        8           
  Partials        6        6           

Impacted Files	Coverage Δ
piptools/repositories/pypi.py	95.56% <100.00%> (+0.03%)	⬆️

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[atugushev]

pip-20.2 release is scheduled to Monday (pypa/pip#8511 (comment))

[AndydeCleyre]

Excellent!

Can you just clarify for me the necessary syncing of tox.ini's envlist with .travis.yml?

[tox]
envlist =
    # NOTE: keep this in sync with the env list in .travis.yml for tox-travis.
    py{27,35,36,37,38,39,py,py3}-pip{20.0,20.1,20.2,latest,master}-coverage
    checkqa
    readme

env:
  # NOTE: keep this in sync with envlist in tox.ini for tox-travis.
  - PIP=latest
  - PIP=20.2  # TODO: update to 20.1 after pip-20.2 being released
  - PIP=20.0

travis.yml doesn't need an explicit 20.1 item because it's covered by latest?

BTW it's good to see you're on top of the pypa/pip#8601 business, thanks!

[atugushev]

@AndydeCleyre

Can you just clarify for me the necessary syncing of tox.ini's envlist with .travis.yml?

That note helps to add a new pip dimension to the matrix using tox-travis. For example, to add a new pip version (let's say 20.2 ) to the CI, we should put version info here:

pip-tools/.travis.yml

Lines 11 to 14 in bd3e735

	env:
	# NOTE: keep this in sync with envlist in tox.ini for tox-travis.
	- PIP=20.0
	- PIP=latest

.. and sync correspondingly here:

pip-tools/tox.ini

Line 4 in bd3e735

py{27,35,36,37,38,39,py,py3}-pip{20.0,20.1,latest,master}-coverage

... and here:

pip-tools/tox.ini

Lines 43 to 48 in bd3e735

	[travis:env]
	PIP =
	20.0: pip20.0
	20.1: pip20.1
	latest: piplatest
	master: pipmaster

travis.yml doesn't need an explicit 20.1 item because it's covered by latest?

Correct. Currently (until 20.2 is being released) 20.1 is the latest release. After the 20.2 is being released we switch the latest version in our configuration in a following-up PR.

BTW it's good to see you're on top of the pypa/pip#8601 business, thanks!

Ha-ha :) I'm just hanging around the new resolver and keep an eye on it.

[atugushev]

Thank you @AndydeCleyre!