scripts: add catkin_pkg and python-empy to Ubuntu prerequisites

Tools/scripts/install-prereqs-ubuntu.sh

@@ -7,10 +7,10 @@ OPT="/opt"
 BASE_PKGS="gawk make git arduino-core curl"
 SITL_PKGS="g++ python-pip python-matplotlib python-serial python-wxgtk2.8 python-scipy python-opencv python-numpy python-pyparsing ccache realpath"
 AVR_PKGS="gcc-avr binutils-avr avr-libc"
-PYTHON_PKGS="pymavlink MAVProxy droneapi"
+PYTHON_PKGS="pymavlink MAVProxy droneapi catkin_pkg"
 PX4_PKGS="python-serial python-argparse openocd flex bison libncurses5-dev \
           autoconf texinfo build-essential libftdi-dev libtool zlib1g-dev \
-          zip genromfs"
+          zip genromfs python-empy"
 BEBOP_PKGS="g++-arm-linux-gnueabihf"
 UBUNTU64_PKGS="libc6:i386 libgcc1:i386 gcc-4.6-base:i386 libstdc++5:i386 libstdc++6:i386"
 ASSUME_YES=false