Only install python3.10 on Ubuntu versions prior to 22.04

We need a minimum of Python 3.10 to get the latest features from the
mitmproxy package. Ubuntu versions after 20.04 provide Python 3.10 or
newer, and so we do not need to install an alternate version from the
deadsnakes PPA.

Author: mcdonnnj

monitor/setup.sh

@@ -112,9 +112,16 @@ if [ "$RUNNER_OS" = "macOS" ]; then
 
 elif [ "$RUNNER_OS" = "Linux" ]; then
 
+  # ubuntu 22.04 and later install python 3.10 or later by default
+  python_package="python3"
+
   # install python 3.10, otherwise ubuntu 20.04 installs 3.8 and we won't get the latest mitmproxy with important bug fixes
-  sudo add-apt-repository ppa:deadsnakes/ppa -y
-  sudo apt install -y python3.10-venv
+  if (( "$(lsb_release --short --release | cut --delimiter='.' --fields=1)" < 22 )); then
+    sudo add-apt-repository ppa:deadsnakes/ppa -y
+    python_package="python3.10"
+  fi
+
+  sudo apt install -y "$python_package"-venv
 
   # create mitmproxyuser, otherwise proxy won't intercept local trafic from the same user
   sudo useradd --create-home mitmproxyuser
@@ -125,7 +132,7 @@ elif [ "$RUNNER_OS" = "Linux" ]; then
                                        git clone -b main https://github.com/mitmproxy/mitmproxy.git && \
                                        cd mitmproxy && \
                                        git checkout 5353df5f1eeaf5fc36d9b5f7024199c888aed116 && \
-                                       python3.10 -m venv venv && \
+                                       "$(command -v python3.10 || command -v python3)" -m venv venv && \
                                        venv/bin/pip install -e ".[dev]" '
 
   sudo cp mitm_plugin.py /home/mitmproxyuser/mitm_plugin.py