The prerm of uwsgi script contains this:

#!/bin/sh

set -e

# Automatically added by dh_installinit

if [ -x "/etc/init.d/uwsgi" ] || [ -e "/etc/init/uwsgi.conf" ]; then

    invoke-rc.d uwsgi stop || exit $?

fi

# End automatically added section

                                                                   

You have a few options:

Edit the prerm script.

The script is usually located at /var/lib/dpkg/uwsgi.prerm.
Do:

sudo sed -i '/invoke-rc.d/ s/^/#/' /var/lib/dpkg/uwsgi.prerm

to comment out the command that stops the service.

Use the conditions in the script to your advantage

Either:

sudo chmod -x /etc/init.d/uwsgi

since the script checks for execute permissions of this script,

Or:

mv /etc/init/uwsgi.conf /etc/init/uwsgi.conf.bak

since the script checks for existence of this Upstart service file.

According to the list of files, the package has /etc/init.d/uwsgi and not the Upstart script.

(Mis)Use policy-rc.d

invoke-rc.d is controlled by policy-rc.d. However, using it directly has a problem. The prerm script is has exit $?, and dpkg doesn't like non-zero exit codes. Hence, this will still require changing the prerm script:

echo 'exit 101' > /usr/sbin/invoke-rc.d

chmod +x /usr/sbin/invoke-rc.d

sed 's/exit/echo/' -i /var/lib/dpkg/uwsgi.prerm

Why did I even answer?

There are some brilliant answers already available: Install packages without starting background processes and services (possibly with some slight adaptation required).