Add ensurepip patch that enables rewheel

ensurepip-rewheel.patch

@@ -0,0 +1,73 @@
+diff -r 15a6be05e970 Lib/ensurepip/__init__.py
+--- a/Lib/ensurepip/__init__.py	Tue Feb 11 11:54:08 2014 +0100
++++ b/Lib/ensurepip/__init__.py	Tue Feb 11 12:42:44 2014 +0100
+@@ -1,8 +1,10 @@
+ import os
+ import os.path
+ import pkgutil
++import shutil
+ import sys
+ import tempfile
++from ensurepip import rewheel
+
+
+ __all__ = ["version", "bootstrap"]
+@@ -38,6 +40,7 @@
+
+     # Install the bundled software
+     import pip
++    args.append('--pre')
+     pip.main(args)
+
+
+@@ -87,20 +90,40 @@
+         # omit pip and easy_install
+         os.environ["ENSUREPIP_OPTIONS"] = "install"
+
++    whls = []
++    rewheel_dir = None
++    # try to see if we have system-wide versions of _PROJECTS
++    dep_records = rewheel.find_system_records([p[0] for p in _PROJECTS])
++    # TODO: check if system-wide versions are the newest ones
++    # if --upgrade is used?
++    if all(dep_records):
++        # if we have all _PROJECTS installed system-wide, we'll recreate
++        # wheels from them and install those
++        rewheel_dir = tempfile.TemporaryDirectory()
++        for dr in dep_records:
++            new_whl = rewheel.rewheel_from_record(dr, rewheel_dir.name)
++            whls.append(os.path.join(rewheel_dir.name, new_whl))
++    else:
++        # if we don't have all the _PROJECTS installed system-wide,
++        # let's just fall back to bundled wheels
++        for project, version in _PROJECTS:
++            whl = os.path.join(
++                os.path.dirname(__file__),
++                "ensurepip",
++                "bundled",
++                "{}-{}-py2.py3-none-any.whl".format(project, version)
++            )
++            whls.append(whl)
++
+     with tempfile.TemporaryDirectory() as tmpdir:
+         # 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))
++        for whl in whls:
++            shutil.copy(whl, tmpdir)
++            additional_paths.append(os.path.join(tmpdir, os.path.basename(whl)))
++        if rewheel_dir:
++            rewheel_dir.cleanup()
+
+         # Construct the arguments to be passed to the pip command
+         args = ["install", "--no-index", "--find-links", tmpdir]