gnumach software package provides Dummy transition package for gnumach-image-*, you can install in your Debian 9 (Stretch) by running the commands given below on the terminal,
$ sudo apt-get update $ sudo apt-get install gnumach
gnumach is installed in your system.
Make ensure the gnumach package were installed using the commands given below,
$ sudo dpkg-query -l | grep gnumach *
You will get with gnumach package name, version, architecture and description in a table
| Distro | Debian 9 stretch |
| Section | Kernels |
| Package | gnumach |
| Version | 2:1.7+git20160921-1 |
| Description | Dummy transition package for gnumach-image-* |
| Sub Section | Kernels |