include the implementation in the depcache

[asottile]

Resolves #1049

Changelog-friendly one-liner: Ensure that depcache considers the python implementation such that (for example) cpython3.6 does not poison the results of pypy3.6.

Contributor checklist

• Provided the tests for the changes. (I did not, this doesn't really fit well into the current testsuite)
• 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 #1050 into master will increase coverage by 0.90%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #1050      +/-   ##
==========================================
+ Coverage   98.60%   99.50%   +0.90%     
==========================================
  Files          34       34              
  Lines        2441     2446       +5     
  Branches      307      306       -1     
==========================================
+ Hits         2407     2434      +27     
+ Misses         25        6      -19     
+ Partials        9        6       -3     

Impacted Files	Coverage Δ
piptools/repositories/pypi.py	95.60% <0.00%> (+2.43%)	⬆️
tests/test_repository_pypi.py	100.00% <0.00%> (+22.66%)	⬆️

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[atugushev]

LGTM 👍

[atugushev]

@asottile thanks!

[asottile]

no problem! thanks for the quick review! this affected us at Lyft :)

[atugushev]

pip-tools v4.4.1 is released.

@asottile happy to know you use pip-tools 😇