[Bug 1505670] Re: "uncaptured python exception"

[cell]

I just ran into this bug, and I think I've figured it out.

/usr/share/squid-deb-proxy-client/apt-avahi-discover is outputting the
URL of my squid-deb-proxy server, but it is also spitting out some
errors:

root at debian:~# /usr/share/squid-deb-proxy-client/apt-avahi-discover 
error: uncaptured python exception, closing channel <AptAvahiClient> ('192.168.2.232', 3142): 9223372036854775807 (<class 'socket.error'>:[Errno 111] Connection refused [/usr/lib/python2.7/asyncore.py|read|83] [/usr/lib/python2.7/asyncore.py|handle_read_event|446] [/usr/lib/python2.7/asyncore.py|handle_connect_event|454])
error: uncaptured python exception, closing channel <AptAvahiClient> ('192.168.2.80', 3142): 9223372036854775807 (<class 'socket.error'>:[Errno 111] Connection refused [/usr/lib/python2.7/asyncore.py|read|83] [/usr/lib/python2.7/asyncore.py|handle_read_event|446] [/usr/lib/python2.7/asyncore.py|handle_connect_event|454])
http://192.168.2.232:8000/]

The problem here is that the errors are going to stdout, not to stderr.
This means apt's Acquire::http::ProxyAutoDetect is not able to figure
out what the proxy URL is.

I have locally modified apt-avahi-discover so that the errors are sent
to stderr, and I have verified that this allows apt's
Acquire::http::ProxyAutoDetect to work correctly.  I have attached this
as a patch.

This patch is enough to fix this bug, but I'm not sure it's ultimately
the best fix for the overall issue.  I think ideally, in the case were
apt-avahi-discover encounters non-fatal errors (and is still able to
produce a working URL), these error should probably just get logged to
syslog, rather than being sent to stderr, because it does make apt's
console output look rather ugly, and the user doesn't need to see any of
that, because if there's a working URL, ultimately they don't care any
other errors.

(This is what apt's output looks like with the patch applied to apt-
avahi-discover:)

0 upgraded, 826 newly installed, 0 to remove and 1 not upgraded.
Need to get 500 MB of archives.
After this operation, 1,554 MB of additional disk space will be used.
Do you want to continue? [Y/n] 
0% [Working]log: error: uncaptured python exception, closing channel <AptAvahiClient> ('192.168.2.80', 3142): 9223372036854775807 (<class 'socket.error'>:[Errno 111] Connection refused [/usr/lib/python2.7/asyncore.py|read|83] [/usr/lib/python2.7/asyncore.py|handle_read_event|446] [/usr/lib/python2.7/asyncore.py|handle_connect_event|454])
log: error: uncaptured python exception, closing channel <AptAvahiClient> ('192.168.2.232', 3142): 9223372036854775807 (<class 'socket.error'>:[Errno 111] Connection refused [/usr/lib/python2.7/asyncore.py|read|83] [/usr/lib/python2.7/asyncore.py|handle_read_event|446] [/usr/lib/python2.7/asyncore.py|handle_connect_event|454])
log: error: uncaptured python exception, closing channel <AptAvahiClient> ('192.168.2.80', 3142): 9223372036854775807 (<class 'socket.error'>:[Errno 111] Connection refused [/usr/lib/python2.7/asyncore.py|read|83] [/usr/lib/python2.7/asyncore.py|handle_read_event|446] [/usr/lib/python2.7/asyncore.py|handle_connect_event|454])
log: error: uncaptured python exception, closing channel <AptAvahiClient> ('192.168.2.232', 3142): 9223372036854775807 (<class 'socket.error'>:[Errno 111] Connection refused [/usr/lib/python2.7/asyncore.py|read|83] [/usr/lib/python2.7/asyncore.py|handle_read_event|446] [/usr/lib/python2.7/asyncore.py|handle_connect_event|454])
Get:1 http://ftp.us.debian.org/debian/ jessie/main alsa-base all 1.0.27+1 [54.3 kB]
Get:2 http://ftp.us.debian.org/debian/ jessie/main libcroco3 amd64 0.6.8-3+b1 [135 kB]
Get:3 http://security.debian.org/ jessie/updates/main libvdpau1 amd64 0.8-3+deb8u1 [33.5 kB]



** Patch added: "Minimal patch to work-around this bug."
   https://bugs.launchpad.net/ubuntu/+source/squid-deb-proxy/+bug/1505670/+attachment/4498637/+files/apt-avahi-discover.patch

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Title:
  "uncaptured python exception"

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