class lc_install(install):
    description = 'Custom Install Process'
user_options = install.user_options[:]
user_options.extend([('manprefix=', None, 'MAN Prefix Path')])

def initialize_options(self):
    self.manprefix = None
install.initialize_options(self)

def finalize_options(self):
    if self.manprefix is None:
        pass
Python: Installing man pages in distutils based project