With the current default branch, test_venv fails every time for me:

[1/1] test_venv
Traceback (most recent call last):
  File "C:\Code\Python\lib\runpy.py", line 160, in _run_module_as_main
    "__main__", fname, loader, pkg_name)
  File "C:\Code\Python\lib\runpy.py", line 73, in _run_code
    exec(code, run_globals)
  File "C:\Code\Python\lib\ensurepip\__main__.py", line 66, in <module>
    main()
  File "C:\Code\Python\lib\ensurepip\__main__.py", line 61, in main
    default_pip=args.default_pip,
  File "C:\Code\Python\lib\ensurepip\__init__.py", line 92, in bootstrap
    _run_pip(args + [p[0] for p in _PROJECTS], additional_paths)
  File "C:\Code\Python\lib\ensurepip\__init__.py", line 28, in _run_pip
    import pip
  File "C:\Users\Tim\AppData\Local\Temp\tmpjltqdgi8\pip-1.5.rc1-py2.py3-none-any.whl\pip\__init__.py", line 10
, in <module>
  File "C:\Users\Tim\AppData\Local\Temp\tmpjltqdgi8\pip-1.5.rc1-py2.py3-none-any.whl\pip\util.py", line 17, in
 <module>
  File "C:\Users\Tim\AppData\Local\Temp\tmpjltqdgi8\pip-1.5.rc1-py2.py3-none-any.whl\pip\_vendor\distlib\versi
on.py", line 14, in <module>
  File "C:\Users\Tim\AppData\Local\Temp\tmpjltqdgi8\pip-1.5.rc1-py2.py3-none-any.whl\pip\_vendor\distlib\compat.py", line 66, in <module>
ImportError: cannot import name 'HTTPSHandler'
test test_venv failed -- Traceback (most recent call last):
  File "C:\Code\Python\lib\test\test_venv.py", line 288, in test_with_pip
    self.run_with_capture(venv.create, self.env_dir, with_pip=True)
  File "C:\Code\Python\lib\test\test_venv.py", line 48, in run_with_capture
    func(*args, **kwargs)
  File "C:\Code\Python\lib\venv\__init__.py", line 359, in create
    builder.create(env_dir)
  File "C:\Code\Python\lib\venv\__init__.py", line 86, in create
    self._setup_pip(context)
  File "C:\Code\Python\lib\venv\__init__.py", line 242, in _setup_pip
    subprocess.check_output(cmd)
  File "C:\Code\Python\lib\subprocess.py", line 618, in check_output
    raise CalledProcessError(retcode, process.args, output=output)
subprocess.CalledProcessError: Command '['C:\\Users\\Tim\\AppData\\Local\\Temp\\tmpt0ca1aqn\\Scripts\\python_d
.exe', '-Im', 'ensurepip', '--upgrade', '--default-pip']' returned non-zero exit status 1

1 test failed:
    test_venv

All virtual Greek to me.