Incorrect dependency in python3-lxml

[Andreas Ronnquist <mailinglists@gusnan.se>]

Trying to install matrix-synapse from backports I run in to the problem
that first it cannot install python3-lxml

( matrix-synapse : Depends: python3-lxml but it is not going to be installed)

and, trying to install this package, I get the following:

gusnan@debian-server:~ > LC_ALL=C sudo apt install -t buster-backports python3-lxml
Reading package lists... Done
Building dependency tree       
Reading state information... Done
Some packages could not be installed. This may mean that you have
requested an impossible situation or if you are using the unstable
distribution that some required packages have not yet been created
or been moved out of Incoming.
The following information may help to resolve the situation:

The following packages have unmet dependencies:
 python3-lxml : Depends: python3 (< 3.6) but 3.7.3-1 is to be installed
                Recommends: python3-bs4 but it is not going to be installed 
                Recommends: python3-html5lib but it is not going to be installed 
E: Unable to correct problems, you have held broken packages.

This has already been reported in the bts:

https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=974684

But if the backporter is different from the package maintainer, they
may not have noticed this, so I report the issue here too, to make it
more visible.

Please make it installable.

/Andreas Rönnquist
mailinglists@gusnan.se
gusnan@debian.org