Add compatibility with pip==19.3 for refactored URL helpers

[atugushev]

Add compatibility with pip==19.3 for the following changes:

1. Move some URL-related functions to utils.urls. pypa/pip#7036
2. Move path_to_url() to utils/urls.py pypa/pip#7075

Changelog-friendly one-liner: Add compatibility with pip==19.3.

Contributor checklist

• Provided the tests for the changes.
• Requested a review from another contributor.
• 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 #910 into master will increase coverage by 0.48%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #910      +/-   ##
==========================================
+ Coverage   98.57%   99.06%   +0.48%     
==========================================
  Files          35       35              
  Lines        2247     2247              
  Branches      288      288              
==========================================
+ Hits         2215     2226      +11     
+ Misses         21       13       -8     
+ Partials       11        8       -3

Impacted Files	Coverage Δ
piptools/utils.py	100% <0%> (+2.04%)	⬆️
piptools/repositories/pypi.py	95.12% <0%> (+3.9%)	⬆️

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[codingjoe]

LGTM 👍
Is there a timeline yet, then the old util functions will be dropped?

[atugushev]

@codingjoe

Thanks for reviewing this! Much appreciated!

Is there a timeline yet, then the old util functions will be dropped?

There is not. It needs to be discussed. Probably it's time to raise an issue.

[atugushev]

@codingjoe

FYI, discussion started here #853.