* travis: fail fast if --with-marvin fails with nose
Install missing dependency pycrypto.
This fixes issue with recent Travis runs which gave incorrect results
around smoketests with simulator where each test run failed with an
error like "nosetests: error: no such option: --with-marvin".
Signed-off-by: Rohit Yadav <rohit.yadav@shapeblue.com>