uwsgi upgrade to python3.7 to fix ImportError: No module named 'encodings' - uwsgi

Question

Honestly, I have no idea what I am doing, so be gentle with me. I am trying to use uwsgi to run my django application on a aws ubuntu instance. I have a virtual environment with python3.7 running, but when I try to run uwsgi. I get this in the logs:
*** Starting uWSGI 2.0.14 (64bit) on [Sun Jan 5 14:51:32 2020] ***
compiled with version: 5.4.0 20160609 on 20 October 2016 05:56:34
os: Linux-4.4.0-109-generic #132-Ubuntu SMP Tue Jan 9 19:52:39 UTC 2018
nodename: ip-172-31-41-139
machine: x86_64
clock source: unix
detected number of CPU cores: 1
current working directory: /
detected binary path: /usr/local/bin/uwsgi
!!! no internal routing support, rebuild with pcre support !!!
uWSGI running as root, you can use --uid/--gid/--chroot options
*** WARNING: you are running uWSGI as root !!! (use the --uid flag) ***
chdir() to /home/ubuntu/web/graff
*** WARNING: you are running uWSGI without its master process manager ***
your processes number limit is 3804
your memory page size is 4096 bytes
detected max file descriptor number: 1024
lock engine: pthread robust mutexes
thunder lock: disabled (you can enable it with --thunder-lock)
uwsgi socket 0 bound to UNIX address /home/ubuntu/web/graffuwsgi.sock fd 3
Python version: 3.5.2 (default, Oct 8 2019, 13:06:37) [GCC 5.4.0 20160609]
Set PythonHome to /home/ubuntu/.virtualenvs/graff
Fatal Python error: Py_Initialize: Unable to get the locale encoding
ImportError: No module named 'encodings'
Here is my uwsgi.conf
# file: /etc/init/graffuwsgi.conf
description "uWSGI server for graff"
start on runlevel [2345]
stop on runlevel [!2345]
respawn
exec /usr/local/bin/uwsgi --home /home/ubuntu/web/graff/ --socket /home/ubuntu/web/graffuwsgi.sock --chmod-socket=666 --module=graff.wsgi --pythonpath /home/ubuntu/web -H /home/ubuntu/.virtualenvs/graff --logto /home/ubuntu/web/logs/graffuwsgi.log --chdir=/home/ubuntu/web/graff --chmod-socket=666
It seems like python3.5 just doesn't work anymore. I feel like I've had to replace python3.5 with 3.7 in several places lately to fix various bugs, and I have it in my head that if I can get uwsgi to run python3.7 instead of 3.5 then that will solve this error too. Anyway, any help is much appreciated.

Answer 1

Looks like your uwsgi is compiled with different python version, make sure you compile with python 3.5
PYTHON=python3.5 uwsgi --build-plugin "/usr/src/uwsgi/plugins/python python35"
mv python35_plugin.so /usr/lib/uwsgi/plugins/python35_plugin.so
chmod 644 /usr/lib/uwsgi/plugins/python35_plugin.so
you can follow this guide:
https://www.paulox.net/2017/04/04/how-to-use-uwsgi-with-python3-6-in-ubuntu/

Answer 2

The source of error is PythonHome (pyhome, venv, home) setting.
See at the official Python docs on Environment variables
Is your path /home/ubuntu/.virtualenvs/graff suited for Python requirements?
In short:
Use pythonpath (pp) and let the system to find modules.
You can set several repeated options in your uwsgi config to custom modules search, eg:
pythonpath = /opt/web2py/
pythonpath = /opt/anaconda/lib/python3.9/site-packages/
So, I had the same error. And it was fixed by editing uwsgi vassal config.
I thing the core of problem that virtual envs are created with symlinks or have some inner relative paths, so an isolated process inside uwsgi could not find modules.