Ok I tested it.
I flashed the latest stable image ( 0.16.0 ), run the webinterface wizard and updated to the latest octoprint.
Then I dist-upgraded to buster.
After that the same arror as in my case - venv seems broken.
(oprint) pi@octopi:~ $ ~/oprint/bin/octoprint serve
Traceback (most recent call last):
File "/home/pi/oprint/bin/octoprint", line 6, in <module>
from pkg_resources import load_entry_point
File "/home/pi/oprint/local/lib/python2.7/site-packages/pkg_resources/__init__.py", line 74, in <module>
File "/home/pi/oprint/local/lib/python2.7/site-packages/pkg_resources/extern/__init__.py", line 61, in load_module
ImportError: The 'packaging.requirements' package is required; normally this is bundled with this package so if you get this warning, consult the packager of your distribution.
(oprint) pi@octopi:~ $
I guess it's safe to say normal users shouldn't dist upgrade to buster.