def _set_current(self, new_current):
new_cur_full_path = self.join(new_current)<EOL>if not os.path.exists(new_cur_full_path):<EOL><INDENT>raise PrefixNotFound(<EOL>'<STR_LIT>' %<EOL>(new_current, self.path)<EOL>)<EOL><DEDENT>if os.path.lexists(self.join('<STR_LIT>')):<EOL><INDENT>os.unlink(self.join('<STR_LIT>'))<EOL><DEDENT>os.symlink(new_current, self.join('<STR_LIT>'))<EOL>self.current = new_current<EOL>
Change the current default prefix, for internal usage

Args:
    new_current(str): Name of the new current prefix, it must already
        exist

Returns:
    None

Raises:
    PrefixNotFound: if the given prefix name does not exist in the
        workdir