Solution: be explicit instead of relying on auto-discovery

Solution: workaround pip _distutils_hack

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Solution: fix it

btw, exclude CI only file from sdist

Solution: use explicit strings

Solution: update

Solution: stop testing it

Solution: be explicit where to find it

Solution: rewrite in easy_install

Keep compatible with earlier pip versions.
Fixes https://github.com/buildout/buildout/issues/598

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Solution: use `python -m pip`

Solution: implement and document it

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Solution: check value explicitely and open corresponding files

Solution: check for existence of namespace directories

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Solution: install proper pip

Solution: add jobs to GH actions and to CircleCI

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Solution: remove useless configs

Solution: add explicit error message

Solution: hide them in doctests

Solution: fix verbosity detection when calling pip

Solution: pass it properly to buildout via a call to sys.exit

Solution: proper os.path.isfile each time it is needed in
make_egg_after_pip_install

some variable rename

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