Not sure what’s going on since I’m not too familiar with glitch, but I was able to bootstrap pip in a remix of your project with the following shell-script:
#!/bin/bash
# Exit early on errors
set -eu
# Python buffers stdout. Without this, you won't see what you "print" in the Activity Logs
export PYTHONUNBUFFERED=true
# Install Python 3 virtual env
VIRTUALENV=.data/venv
if [ ! -d $VIRTUALENV ]; then
python3 -m venv $VIRTUALENV
fi
if [ ! -f $VIRTUALENV/bin/pip ]; then
curl --silent --show-error --retry 5 https://bootstrap.pypa.io/get-pip.py | $VIRTUALENV/bin/python
fi
# Install the requirements
$VIRTUALENV/bin/pip install -r requirements.txt
# Run a glorious Python 3 server
$VIRTUALENV/bin/python3 server.py