update python version for appimage

packaging/pack_linux_docker.sh

@@ -2,7 +2,7 @@
 
 CENTOS_VERSION=${1:-"7"}                                     # Shouldn't influence on the results. We need it only to unpack AppImage. Better to keep 7 for manylinux2014
 MANYLINUX_VERSION=${2:-"2014"}                               # This means that downloaded python version has been built in CentOS 7. See https://www.python.org/dev/peps/pep-0599/ for details.
-PYTHON_VERSION=${3:-"3.8.18"}                                # Three digits. Before build check the latest available versions on https://github.com/niess/python-appimage/tags
+PYTHON_VERSION=${3:-"3.8.19"}                                # Three digits. Before build check the latest available versions on https://github.com/niess/python-appimage/tags
 CLUSTER_VERSION=${4:-"master"} #-`git rev-parse --abbrev-ref HEAD`}  # Will be always pulled from GitHub. Doesn't support build from local directory
 
 # WORKING_DIR=$( cd "$( dirname "${BASH_SOURCE[0]}" )" && pwd )