Supervisor: Depends: python-meld3 but it is not installable how to fix?

Question

Debian

Tell me how to deal with the supervisor installation error in Debian 9

lsb_release -a
No LSB modules are available.
Distributor ID: Debian
Description: Debian GNU/Linux 9.9 (stretch)
Release: 9.9
Codename: stretch

sudo apt install supervisor -y
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:
supervisor : Depends: python-meld3 but it is not installable
E: Unable to correct problems, you have held broken packages.

I visited typical senseless events that have never been repaired in this life ...

sudo apt-get update
sudo apt-get clean
sudo apt-get autoremove
sudo apt --fix-broken install

How to live with it? how to install this supervisor?