There's an error in the new code: self has no log_info attribute.
Also, I had to add a ) at the end of demo.py before it would run.

As detailed in my comments below, I found some of the messages
from the demo (perhaps actually from the server?) confusing.

Steps
=====

Updated to the latest, 8649 : cafa177776bb.
By the way I looked for the new documentation when your reported it changed for my
other bug, but didn't see it.  It (r8648) did show up a couple of hours later.

Then I applied the change you suggested before line 284 in roundup/scripts/roundup_server.py.  Here's the transcript, with added # commentary.

# On the terminal where I launched the demo yesterday
# Still hadn't returned to prompt, and so probably running.
^CKeyboard Interrupt: exiting
ross@barley:/usr/local/src/roundup$ date; python3 ./demo.py -b sqlite
Mon 18 May 2026 03:25:25 PM PDT
Traceback (most recent call last):
  File "/usr/local/src/roundup/./demo.py", line 5, in <module>
    from roundup.demo import main
  File "/usr/local/src/roundup/roundup/demo.py", line 137
    sys.exit(2)
    ^
SyntaxError: invalid syntax
# Edited demo.py to fix the apparent missing ) at the end of the previous line
ross@barley:/usr/local/src/roundup$ date; python3 ./demo.py -b sqlite
Mon 18 May 2026 03:28:30 PM PDT
Error: Arguments are not allowed when running an existing demo.
       Use the 'nuke' command to start over.
# Since I don't think I am running the demo, since I ^C'd it,
# this error surprised me.  It also made me wonder if it was still
# running, in which case it would have loaded the code before
# the recent edits.  Or it could just mean some lock or configuration
# files were still around.
ross@barley:/usr/local/src/roundup$ date; python3 ./demo.py nuke
Mon 18 May 2026 03:28:53 PM PDT
Initializing demo instance in:
    /usr/local/src/roundup/demo
Nuking directory left from the previous demo instance.
Trying to set up web server on port 8917 ...
# same port, which argues against the previous instance being active
should be ok.

# ... [boilerplate deleted]
# but it says to change backend types I must use nuke.
# but I just used nuke...

^CKeyboard Interrupt: exiting
ross@barley:/usr/local/src/roundup$ date; python3 ./demo.py nuke
Mon 18 May 2026 03:29:34 PM PDT
Initializing demo instance in:
    /usr/local/src/roundup/demo
Nuking directory left from the previous demo instance.
Trying to set up web server on port 8917 ...
should be ok.

Demo Tracker Home: /usr/local/src/roundup/demo
Server running - connect to:

    http://localhost:8917/demo/

# ... deletions
# At this point I pointed Firefox at the port

127.0.0.1 - - [18/May/2026 15:31:10] "GET / HTTP/1.1" 302 -
127.0.0.1 - - [18/May/2026 22:31:11] "GET /demo/index HTTP/1.1" 200 -
127.0.0.1 - - [18/May/2026 22:31:11] "GET /demo/@@file/style.css HTTP/1.1" 200 -
127.0.0.1 - - [18/May/2026 22:31:11] "GET /demo/@@file/classhelper.js HTTP/1.1" 200 -
127.0.0.1 - - [18/May/2026 22:31:11] "GET /demo/@@file/datecopy.min.js HTTP/1.1" 200 -
127.0.0.1 - - [18/May/2026 22:31:11] "GET /demo/rest HTTP/1.1" 403 -
127.0.0.1 - - [18/May/2026 22:31:12] "GET /favicon.ico HTTP/1.1" 200 -
# and here it stopped for awhile
# I don't think I touched any of the controls on the window, and certainly
# did not try to login
127.0.0.1 - - [18/May/2026 22:32:12] Request timed out: timeout('timed out')
# after seeing the previous message, I did try to login as demo
127.0.0.1 - - [18/May/2026 22:32:23] "POST /demo/ HTTP/1.1" 302 -
127.0.0.1 - - [18/May/2026 22:32:23] "GET /demo/index?%40ok_message=Welcome+demo%21 HTTP/1.1" 200 -
127.0.0.1 - - [18/May/2026 22:32:23] "GET /demo/rest HTTP/1.1" 200 -
127.0.0.1 - - [18/May/2026 22:32:23] "GET /favicon.ico HTTP/1.1" 200 -
----------------------------------------
Exception occurred during processing of request from ('127.0.0.1', 43348)
Traceback (most recent call last):
  File "/usr/local/src/roundup/roundup/scripts/roundup_server.py", line 275, in run_cgi
    self.inner_run_cgi()
  File "/usr/local/src/roundup/roundup/scripts/roundup_server.py", line 420, in inner_run_cgi
    self.wfile.write(data)
  File "/usr/lib/python3.9/socketserver.py", line 799, in write
    self._sock.sendall(b)
BrokenPipeError: [Errno 32] Broken pipe

# Since there is no "Client has gone" message, it seems the new
# except clause didn't activate. However it's the next reported 
# error, and so this may just reflect the order in which nested errors
# are reported.
# Line 275 is reported as the most 
# recent call, and it certainly looks as if it's covered by the new except

# The next failure definitely reflects the new code.
# Unfortunately, the new code has an error.


During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/usr/lib/python3.9/socketserver.py", line 616, in process_request
    self.finish_request(request, client_address)
  File "/usr/lib/python3.9/socketserver.py", line 360, in finish_request
    self.RequestHandlerClass(request, client_address, self)
  File "/usr/lib/python3.9/socketserver.py", line 720, in __init__
    self.handle()
  File "/usr/local/src/roundup/roundup/scripts/roundup_server.py", line 333, in handle_method_wrapper
    http_.server.BaseHTTPRequestHandler.handle(self)
  File "/usr/lib/python3.9/http/server.py", line 436, in handle
    self.handle_one_request()
  File "/usr/lib/python3.9/http/server.py", line 422, in handle_one_request
    method()
  File "/usr/local/src/roundup/roundup/scripts/roundup_server.py", line 285, in run_cgi
    self.log_info("Client has gone: %s", e)
AttributeError: 'RequestHandler' object has no attribute 'log_info'
----------------------------------------
127.0.0.1 - - [18/May/2026 22:32:23] "GET /demo/?%40template=translation&properties=apply%2Ccancel%2Cnext%2Cprev%2Csearch%2Creset%2CInfo+on+%7BclassName%7D+-+%7BitemDesignator%7D+-+Classhelper HTTP/1.1" 200 -
127.0.0.1 - - [18/May/2026 22:33:23] Request timed out: timeout('timed out')
# timeouts seem to be after 60s