FEAT: vendorize keyring, tested on Linux.
STY: move local import that can be moved out.
BUG: ensure we never actually modify keyring.
BUG: ensure we properly set up keyring when writing the file.
FEAT: add simple function to check whether we use epd_auth or epd_username.
REF: extract setting up password in keyring if not set.

We will need to re-use this feature for EPD_auth -> EPD_username
conversion.
REF: consolidate keyring get/set.
FEAT: add a function to convert from EPD_auth to EPD_username when required.
BUG: always use sys.exit in main_noexc.
TST: add function test for EPD_auth -> EPD_username conversion.
BUG: fix without_any_configuration decorator.
ENH: include keyring in the list of subpackages installed.
BUG: fix function test suite on 2.6.
ENH: --config now prints the keyring backend.
BUG: fix functional test suite on 2.6.
FEAT: vendorize pywin32-ctypes.
ENH: use vendorized pywin32ctypes in keyring.
BUG: remove tests of vendorized pywin32ctypes added by accident.
BUG: fix keyring win32ctypes import on non-win32 platform.
BUG: properly handle platform != (windows,osx) in keyring backend setup.