Fix initial installation process

Signed-off-by: Alfredos-Panagiotis Damkalis <fredy@fredy.gr>

contrib/refresh-requirements.sh

@@ -21,6 +21,7 @@ EXCLUDE_REGEXP="^\\(pkg[-_]resources\\|satnogs-db\\)"
 COMPATIBLE_REGEXP="^\\(satnogs-decoders\\)"
 VIRTUALENV_DIR=$(mktemp -d)
 PIP_COMMAND="$VIRTUALENV_DIR/bin/pip"
+PYTHON_VERSION="3.9"
 REQUIREMENTS="
 comm
 grep
@@ -45,7 +46,7 @@ if [ -n "$has_missing" ]; then
 fi
 
 # Create virtualenv
-virtualenv "$VIRTUALENV_DIR"
+virtualenv -p python$PYTHON_VERSION "$VIRTUALENV_DIR"
 
 # Install package with dependencies
 "$PIP_COMMAND" install --no-cache-dir --force-reinstall .

pyproject.toml

@@ -0,0 +1,2 @@
+[build-system]
+requires = ["setuptools", "wheel"]