Mike, Thanks very much for your advice! Using the boot repair tool you recommended I was able to get my system to boot, but the problems with the Gparted manual and the FAQ remain. I don't think it would be in the best interest of the Linux community to mark this problem as solved until the problems with the GParted manual are addressed.
I see that there is a way to report documentation problems for GParted with Bugzilla, so I can try posting a link to this thread as a new bug.
My computer has other problems now, but at least the Lubuntu partition seems to boot properly so the remaining problems will be topics for another forum.
Here are some details of the additional things I did that resulted in a system that boots properly:
First I burned a copy of the 2017 version of System Rescue CD to see if I would have any more success with it than the old version I had been using. I got the same results. The chroot syntax described in the GParted manual displays the same error message. Specifying bash eliminates the error message, but chroot will not accept zsh, even though both shell files are in the same directory.
Then I went to the link in the previous post and followed those instructions, burning a copy of the Boot-Repair-Disk. I left most of the menus in Boot-Repair-Disk at their default, although I specified my Lubuntu partition for the boot flag. After that the system would boot successfully, but the Grub boot menu that was displayed had about a dozen choices and none of the descriptions made any sense (except for Memtest). The Lubuntu partition seemed to work properly.
My next step was to run the update from Lubuntu 14.04 to 16.04. That fixed the Grub boot menu so the choices make sense now. There were some errors while trying to make the update, but after several iterations it tells me everything is up to date. The only major problem I see now is that the system hangs when I try to shut it down.
What happened to break your system? Knowing that might help in it's recovery.
The Lubuntu installation on this computer worked without major problems before I used GParted. Grub was set up to display a menu for choosing which partition to boot. I wanted to update Lubuntu from version 14.04 to 16.04, but the update failed because there was not enough free space in the partition to download all of the update files. It seemed like the easiest way to solve the problem would be with GParted. There was some unallocated space on the drive but it was not adjacent to the Lubuntu partition.
It had been so long since I used the other bootable partition on this disk that I don't remember if it worked. After using Boot-Repair-Disk it does not boot. I get the message "The disk drive for /data1 is not ready yet or not present..." . Apparently it was this partition that produced the error message I saw after I followed the instructions in the GParted manual. There was no Grub boot menu at that point. (I am not concerned about trying to fix the installation on this partition.)