code: @Nullable
    public static String removePropertyValue (@Nonnull final String sKey)
    {
      final String ret = IPrivilegedAction.systemClearProperty (sKey).invokeSafe ();
      if (LOGGER.isDebugEnabled ())
        if (ret != null)
          LOGGER.debug ("Removed system property '" + sKey + "' with value '" + ret + "'");
        else
          LOGGER.debug ("Remove system property '" + sKey + "' failed");
      return ret;
    }
docs: Remove a system property value under consideration of an eventually present
  {@link SecurityManager}.
  
  @param sKey
  The key of the system property to be removed. May not be
  <code>null</code>.
  @return the previous string value of the system property, or
  <code>null</code> if there was no property with that key.