Tools: add psutil for kill_tasks_psutil in sim_vehicle.py

Tools/environment_install/install-prereqs-ubuntu.sh

@@ -98,7 +98,7 @@ if [[ $SKIP_AP_EXT_ENV -ne 1 ]]; then
 fi
 ARM_LINUX_PKGS="g++-arm-linux-gnueabihf pkg-config-arm-linux-gnueabihf"
 # python-wxgtk packages are added to SITL_PKGS below
-SITL_PKGS="libtool libxml2-dev libxslt1-dev ${PYTHON_V}-dev ${PYTHON_V}-pip ${PYTHON_V}-setuptools ${PYTHON_V}-numpy ${PYTHON_V}-pyparsing"
+SITL_PKGS="libtool libxml2-dev libxslt1-dev ${PYTHON_V}-dev ${PYTHON_V}-pip ${PYTHON_V}-setuptools ${PYTHON_V}-numpy ${PYTHON_V}-pyparsing ${PYTHON_V}-psutil"
 # add some packages required for commonly-used MAVProxy modules:
 if [[ $SKIP_AP_GRAPHIC_ENV -ne 1 ]]; then
   SITL_PKGS="$SITL_PKGS xterm ${PYTHON_V}-matplotlib ${PYTHON_V}-serial ${PYTHON_V}-scipy ${PYTHON_V}-opencv libcsfml-dev libcsfml-audio${SITLCFML_VERSION} libcsfml-dev libcsfml-graphics${SITLCFML_VERSION} libcsfml-network${SITLCFML_VERSION} libcsfml-system${SITLCFML_VERSION} libcsfml-window${SITLCFML_VERSION} libsfml-audio${SITLFML_VERSION} libsfml-dev libsfml-graphics${SITLFML_VERSION} libsfml-network${SITLFML_VERSION} libsfml-system${SITLFML_VERSION} libsfml-window${SITLFML_VERSION} ${PYTHON_V}-yaml"