Following the plan in https://bugs.debian.org/1085728, matrix-synapse
needs to be updated to cope with this package renaming.  It looks as
though the first step is to upgrade to 1.120.0, since that has this in
its CHANGES.md:

  - Support new package name of PyPI package `python-multipart` 0.0.13 so that distro packagers do not need to work around name conflict with PyPI package `multipart`. ([\#17932](https://github.com/element-hq/synapse/issues/17932))

(It also fixes its tests to work with the latest version of Twisted,
which is a problem for our twisted package at the moment - see
#1088631.)

After that, this package's Build-Depends need a slight adjustment, as
follows:

diff --git a/debian/control b/debian/control
index 2e75e937..5795597b 100644
--- a/debian/control
+++ b/debian/control
@@ -76,7 +76,8 @@ Build-Depends:
  python3-lxml (>= 4.2.0),
  python3-matrix-common (>= 1.3.0~),
  python3-msgpack (>= 0.5.0),
- python3-multipart (>= 0.0.9),
+ python3-multipart (>= 0.0.9) | python3-python-multipart,
+ python3-multipart (<< 0.1) | python3-python-multipart,
  python3-nacl (>= 1.2.1),
  python3-netaddr (>= 0.7.18),
  python3-openssl (>= 0.14),

Once python3-python-multipart reaches testing, that entry in
Build-Depends can be simplified at your leisure to just
"python3-python-multipart".

Thanks,

Source: matrix-synapse
Source-Version: 1.121.0-2

Andrej uploaded this, and it all seems to be fine now:

matrix-synapse (1.121.0-2) unstable; urgency=medium

  [ Colin Watson ]
  * Handle python3-multipart → python3-python-multipart renaming.