ImportError: No module named em

Traceback (most recent call last):
File "/opt/ros/kinetic/share/gencpp/cmake/../../../lib/gencpp/gen_cpp.py", line 41, in <module>
import genmsg.template_tools
File "/opt/ros/kinetic/lib/python2.7/dist-packages/genmsg/template_tools.py", line 39, in <module>
import em
ImportError: No module named em
crazyflie_ros/crazyflie_driver/CMakeFiles/crazyflie_driver_generate_messages_cpp.dir/build.make:215: recipe for target '/home/ubuntu/crazyswarm/ros_ws/devel/include/crazyflie_driver/sendPacket.h' failed
make[2]: *** [/home/ubuntu/crazyswarm/ros_ws/devel/include/crazyflie_driver/sendPacket.h] Error 1
Traceback (most recent call last):
File "/opt/ros/kinetic/share/gencpp/cmake/../../../lib/gencpp/gen_cpp.py", line 41, in <module>
import genmsg.template_tools
File "/opt/ros/kinetic/lib/python2.7/dist-packages/genmsg/template_tools.py", line 39, in <module>
import em
ImportError: No module named em