Section 158. Real property of authorities exempt from levy

All real
  property of an authority shall be exempt from levy and sale by virtue of
  an execution, and no execution or other  judicial  process  shall  issue
  against  the  same,  nor  shall  any  judgment against an authority be a
  charge or lien upon its  real  property;  provided,  however,  that  the
  provisions  of  this  section  shall  not apply to or limit the right of
  obligees to foreclose or otherwise enforce any mortgage of an  authority
  or  the  right of obligees to pursue any remedies for the enforcement of
  any covenant of an authority or of  any  pledge  or  lien  given  by  an
  authority on its rents, fees or revenues.