def use_winlegacy():
if sys.platform != '<STR_LIT:win32>':<EOL><INDENT>plat = platform.system() or sys.platform<EOL>if plat == '<STR_LIT>':<EOL><INDENT>plat = '<STR_LIT>'<EOL><DEDENT>raise EnvironmentError('<STR_LIT>' % plat)<EOL><DEDENT>with _backend_lock:<EOL><INDENT>if _module_values['<STR_LIT>'] is not None:<EOL><INDENT>raise RuntimeError(<EOL>'<STR_LIT>'<EOL>)<EOL><DEDENT>_module_values['<STR_LIT>'] = '<STR_LIT>'<EOL><DEDENT>
Forces use of the legacy Windows CryptoAPI. This should only be used on
Windows XP or for testing. It is less full-featured than the Cryptography
Next Generation (CNG) API, and as a result the elliptic curve and PSS
padding features are implemented in pure Python. This isn't ideal, but it
a shim for end-user client code. No one is going to run a server on Windows
XP anyway, right?!

:raises:
    EnvironmentError - when this function is called on an operating system other than Windows
    RuntimeError - when this function is called after another part of oscrypto has been imported