python-psutil cannot be cross built from source, because it
Build-Depends on the host architecture Python interpreter development
package. The host Python fails postinst as it attempts byte compilation.
What it really wanted was a build architecture interpreter and a host
architecture development environment. This is usually expressed as
libpython3-all-dev and python3-all-dev:native. Once fixing this, it also
runs into #1121810. I'm attaching a patch for your convenience. Please
consider applying it.

Helmut