A workaround for Ubuntu's ensurepip problem.

ensure-ensurepip.py

"""
This is a script for working around the lack of ensurepip in
Ubuntu's system Python installs.
See: https://bugs.launchpad.net/ubuntu/+source/python3.4/+bug/1290847

An alternative is the following:

  $ python3 -m venv --without-pip my-venv
  $ curl https://bootstrap.pypa.io/get-pip.py
  $ my-venv/bin/python3 get-pip.py
"""

import os
import os.path
import site
import sys
import urllib.request


# This should be compatible back a ways (3.8+ isn't).
ENSUREPIP_URL = 'https://github.com/python/cpython/raw/3.7/Lib/ensurepip'
FILES = (
    '__init__.py',
    '__main__.py',
    '_uninstall.py',
    '_bundled/pip-19.2.3-py2.py3-none-any.whl',
    '_bundled/setuptools-41.2.0-py2.py3-none-any.whl',
)


def _download_ensurepip(pkgdir):
    print('installing ensurepip from {}'.format(ENSUREPIP_URL))
    os.makedirs(os.path.join(pkgdir, '_bundled'))
    for name in FILES:
        urllib.request.urlretrieve(
            ENSUREPIP_URL + '/' + name,
            os.path.join(pkgdir, os.path.normcase(name)),
        )


def _ensure_ensurepip(stdlib):
    try:
        import ensurepip
    except ImportError:
        pkgdir = os.path.join(stdlib, 'ensurepip')
        # We cannot install to site.USER_SITE since venv ignores it.
        try:
            _download_ensurepip(pkgdir)
        except PermissionError:
            msg = 'ERROR: could not open "{}/" for writing (need sudo?)'
            print(msg.format(pkgdir), file=sys.stderr)
            return
        print('ensurepip installed at {!r}'.format(pkgdir))
    else:
        # XXX Support --force?
        # XXX Make sure it's the right one?
        print('ensurepip already installed: {!r}'.format(ensurepip.__file__))
        return


##################################
# the script

def main():
    stdlib = os.path.dirname(site.__file__)
    _ensure_ensurepip(stdlib)


if __name__ == '__main__':
    main()