Implement PEP 477 - Backport ensurepip (PEP 453) to 2.7

* Backports ensurepip to the 2.7 branch
* Backports some of the improved documentation to the 2.7 branch.
* Adds a private backport of the 3.x mock library as test._mock_backport
  to enable saner testing of ensurepip.

Key Differences from 3.x:

* Ensurepip does not have any Makefile integration, specifically
  it is not ran by default in the Makefile.
* There is no venv module in 2.7, so downstream distributors can
  completely disable ensurepip, ideally with a message redirecting
  to the correct way to install pip.
* To match the ``python`` command in 2.7, ensurepip will install
  the unversioned ``pip`` command as well.
* No-op and hide --default-pip and add --no-default-pip to restore
  the 3.x behavor on 2.7.

1 files changed, 227 insertions, 0 deletions

diff --git a/Lib/ensurepip/__init__.py b/Lib/ensurepip/__init__.py
new file mode 100644
index 0000000..b4bb68e
--- /dev/null
+++ b/Lib/ensurepip/__init__.py
@@ -0,0 +1,227 @@
+#!/usr/bin/env python2
+from __future__ import print_function
+
+import os
+import os.path
+import pkgutil
+import shutil
+import sys
+import tempfile
+
+
+__all__ = ["version", "bootstrap"]
+
+
+_SETUPTOOLS_VERSION = "3.6"
+
+_PIP_VERSION = "1.5.6"
+
+# pip currently requires ssl support, so we try to provide a nicer
+# error message when that is missing (http://bugs.python.org/issue19744)
+_MISSING_SSL_MESSAGE = ("pip {} requires SSL/TLS".format(_PIP_VERSION))
+try:
+    import ssl
+except ImportError:
+    ssl = None
+
+    def _require_ssl_for_pip():
+        raise RuntimeError(_MISSING_SSL_MESSAGE)
+else:
+    def _require_ssl_for_pip():
+        pass
+
+_PROJECTS = [
+    ("setuptools", _SETUPTOOLS_VERSION),
+    ("pip", _PIP_VERSION),
+]
+
+
+def _run_pip(args, additional_paths=None):
+    # Add our bundled software to the sys.path so we can import it
+    if additional_paths is not None:
+        sys.path = additional_paths + sys.path
+
+    # Install the bundled software
+    import pip
+    pip.main(args)
+
+
+def version():
+    """
+    Returns a string specifying the bundled version of pip.
+    """
+    return _PIP_VERSION
+
+
+def _disable_pip_configuration_settings():
+    # We deliberately ignore all pip environment variables
+    # when invoking pip
+    # See http://bugs.python.org/issue19734 for details
+    keys_to_remove = [k for k in os.environ if k.startswith("PIP_")]
+    for k in keys_to_remove:
+        del os.environ[k]
+    # We also ignore the settings in the default pip configuration file
+    # See http://bugs.python.org/issue20053 for details
+    os.environ['PIP_CONFIG_FILE'] = os.devnull
+
+
+def bootstrap(root=None, upgrade=False, user=False,
+              altinstall=False, default_pip=True,
+              verbosity=0):
+    """
+    Bootstrap pip into the current Python installation (or the given root
+    directory).
+
+    Note that calling this function will alter both sys.path and os.environ.
+    """
+    if altinstall and default_pip:
+        raise ValueError("Cannot use altinstall and default_pip together")
+
+    _require_ssl_for_pip()
+    _disable_pip_configuration_settings()
+
+    # By default, installing pip and setuptools installs all of the
+    # following scripts (X.Y == running Python version):
+    #
+    #   pip, pipX, pipX.Y, easy_install, easy_install-X.Y
+    #
+    # pip 1.5+ allows ensurepip to request that some of those be left out
+    if altinstall:
+        # omit pip, pipX and easy_install
+        os.environ["ENSUREPIP_OPTIONS"] = "altinstall"
+    elif not default_pip:
+        # omit pip and easy_install
+        os.environ["ENSUREPIP_OPTIONS"] = "install"
+
+    tmpdir = tempfile.mkdtemp()
+    try:
+        # Put our bundled wheels into a temporary directory and construct the
+        # additional paths that need added to sys.path
+        additional_paths = []
+        for project, version in _PROJECTS:
+            wheel_name = "{}-{}-py2.py3-none-any.whl".format(project, version)
+            whl = pkgutil.get_data(
+                "ensurepip",
+                "_bundled/{}".format(wheel_name),
+            )
+            with open(os.path.join(tmpdir, wheel_name), "wb") as fp:
+                fp.write(whl)
+
+            additional_paths.append(os.path.join(tmpdir, wheel_name))
+
+        # Construct the arguments to be passed to the pip command
+        args = ["install", "--no-index", "--find-links", tmpdir]
+        if root:
+            args += ["--root", root]
+        if upgrade:
+            args += ["--upgrade"]
+        if user:
+            args += ["--user"]
+        if verbosity:
+            args += ["-" + "v" * verbosity]
+
+        _run_pip(args + [p[0] for p in _PROJECTS], additional_paths)
+    finally:
+        shutil.rmtree(tmpdir, ignore_errors=True)
+
+
+def _uninstall_helper(verbosity=0):
+    """Helper to support a clean default uninstall process on Windows
+
+    Note that calling this function may alter os.environ.
+    """
+    # Nothing to do if pip was never installed, or has been removed
+    try:
+        import pip
+    except ImportError:
+        return
+
+    # If the pip version doesn't match the bundled one, leave it alone
+    if pip.__version__ != _PIP_VERSION:
+        msg = ("ensurepip will only uninstall a matching version "
+               "({!r} installed, {!r} bundled)")
+        print(msg.format(pip.__version__, _PIP_VERSION), file=sys.stderr)
+        return
+
+    _require_ssl_for_pip()
+    _disable_pip_configuration_settings()
+
+    # Construct the arguments to be passed to the pip command
+    args = ["uninstall", "-y"]
+    if verbosity:
+        args += ["-" + "v" * verbosity]
+
+    _run_pip(args + [p[0] for p in reversed(_PROJECTS)])
+
+
+def _main(argv=None):
+    if ssl is None:
+        print("Ignoring ensurepip failure: {}".format(_MISSING_SSL_MESSAGE),
+              file=sys.stderr)
+        return
+
+    import argparse
+    parser = argparse.ArgumentParser(prog="python -m ensurepip")
+    parser.add_argument(
+        "--version",
+        action="version",
+        version="pip {}".format(version()),
+        help="Show the version of pip that is bundled with this Python.",
+    )
+    parser.add_argument(
+        "-v", "--verbose",
+        action="count",
+        default=0,
+        dest="verbosity",
+        help=("Give more output. Option is additive, and can be used up to 3 "
+              "times."),
+    )
+    parser.add_argument(
+        "-U", "--upgrade",
+        action="store_true",
+        default=False,
+        help="Upgrade pip and dependencies, even if already installed.",
+    )
+    parser.add_argument(
+        "--user",
+        action="store_true",
+        default=False,
+        help="Install using the user scheme.",
+    )
+    parser.add_argument(
+        "--root",
+        default=None,
+        help="Install everything relative to this alternate root directory.",
+    )
+    parser.add_argument(
+        "--altinstall",
+        action="store_true",
+        default=False,
+        help=("Make an alternate install, installing only the X.Y versioned"
+              "scripts (Default: pipX, pipX.Y, easy_install-X.Y)"),
+    )
+    parser.add_argument(
+        "--default-pip",
+        action="store_true",
+        default=True,
+        dest="default_pip",
+        help=argparse.SUPPRESS,
+    )
+    parser.add_argument(
+        "--no-default-pip",
+        action="store_false",
+        dest="default_pip",
+        help=("Make a non default install, installing only the X and X.Y "
+              "versioned scripts."),
+    )
+
+    args = parser.parse_args(argv)
+
+    bootstrap(
+        root=args.root,
+        upgrade=args.upgrade,
+        user=args.user,
+        verbosity=args.verbosity,
+        altinstall=args.altinstall,
+        default_pip=args.default_pip,
+    )