[Python-modules-team] Bug#866180: [mod-wsgi] "Bad Request" with moinmoin while saving a page

[Lars Kruse]

Package: mod-wsgi
Version: 4.5.11-1
Severity: normal

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Recently I upgrade my wiki server (based on moinmoin) from jessie to buster.
Thank you for that release!

Sadly I received notifications from multiple users in multiple moin wikis
afterwards. They received the following message when trying to save a page:

  Bad Request
  The browser (or proxy) sent a request that this server could not understand.

Not all wiki pages were affected - but all affected wiki pages showed this
behaviour reliably with every save request.

I chased down the problem to the package libapache2-mod-wsgi.
With the version from buster (4.5.11-1) the problem occurred.
With the version from jessie (4.4.13-0.1) the problem disappeared.
I also tried another version (4.5.7-1) from snapshot.debian.org - this worked,
as well.
Switching back and forth between these versions showed predictable behaviour.

I bisected the (few) commits of mod-wsgi's upstream repository.
The problem started here:
 https://github.com/GrahamDumpleton/mod_wsgi/commit/4e757103334765691fab24362a41c870c990be8f
I went away with this commit:
 https://github.com/GrahamDumpleton/mod_wsgi/commit/9192fd36620ca7515954e4ef2d21458c8563ebe2

The host is running amd64.

Thank you for your time.

Cheers,
Lars