def shell_check(self, argument):
    """ Checks for special characters in arguments that are part of shell
    commands.

    Args:
      argument: A str, the argument to be checked.
    Raises:
      BadConfigurationException if single quotes are present in argument.
    """
    if argument in '\'':
      raise BadConfigurationException("Single quotes (') are not allowed " + \
        "in filenames.")
dataset/ETHPy150Open AppScale/appscale/AppDashboard/lib/app_dashboard_helper.py/AppDashboardHelper.shell_check/swapped operands of `in`