Load a kext by forking into kextload.

def LegacyKextload(self, cf_bundle_url, dependency_kext):
    """Load a kext by forking into kextload."""
    _ = dependency_kext
    error_code = OS_SUCCESS
    cf_path = self.dll.CFURLCopyFileSystemPath(cf_bundle_url, POSIX_PATH_STYLE)
    path = self.CFStringToPystring(cf_path)
    self.dll.CFRelease(cf_path)
    try:
      subprocess.check_call(['/sbin/kextload', path])
    except subprocess.CalledProcessError as cpe:
      logging.debug('failed to load %s:%s', path, str(cpe))
      error_code = -1
    return error_code