Issue2251

We need to support jython -m ensurepip as follows:

1) Change the installer so this invocation is performed, by default (but can be checked off if desired)

2) Windows is currently running into this problem, no doubt because it assumes that the system is posix instead of nt, based on os.name/os._name issues:

Traceback (most recent call last):
  File "<string>", line 1, in <module>
  File "C:\jythondev\jython27\dist\Lib\runpy.py", line 175, in run_module
    return _run_module_code(code, init_globals, run_name,
  File "C:\jythondev\jython27\dist\Lib\runpy.py", line 81, in _run_module_code
    _run_code(code, mod_globals, init_globals,
  File "C:\jythondev\jython27\dist\Lib\runpy.py", line 72, in _run_code
    exec code in run_globals
  File "C:\jythondev\jython27\dist\Lib\ensurepip\__main__.py", line 4, in <module>
    ensurepip._main()
  File "C:\jythondev\jython27\dist\Lib\ensurepip\__init__.py", line 220, in _main
    bootstrap(
  File "C:\jythondev\jython27\dist\Lib\ensurepip\__init__.py", line 123, in bootstrap
    _run_pip(args + [p[0] for p in _PROJECTS], additional_paths)
  File "C:\jythondev\jython27\dist\Lib\ensurepip\__init__.py", line 45, in _run_pip
    import pip
  File "c:\users\jim\appdata\local\temp\tmpzhzoqk\pip-1.6-py2.py3-none-any.whl\pip\__init__.py", line 10, in <module>
  File "c:\users\jim\appdata\local\temp\tmpzhzoqk\pip-1.6-py2.py3-none-any.whl\pip\util.py", line 17, in <module>
  File "c:\users\jim\appdata\local\temp\tmpzhzoqk\pip-1.6-py2.py3-none-any.whl\pip\locations.py", line 109, in <module>
  File "c:\users\jim\appdata\local\temp\tmpzhzoqk\pip-1.6-py2.py3-none-any.whl\pip\locations.py", line 71, in _get_build
_prefix
  File "c:\users\jim\appdata\local\temp\tmpzhzoqk\pip-1.6-py2.py3-none-any.whl\pip\locations.py", line 65, in __get_user
name
  File "C:\jythondev\jython27\dist\Lib\pwd.py", line 18, in <module>
    raise ImportError, 'pwd module not supported on Windows'
ImportError: pwd module not supported on Windows

Triaged to urgent since this should be a full part of RC1

Depends on #1491 (windows native launcher, aka jython.exe)

Fixed as of https://hg.python.org/jython/rev/5d62f637a8d1