System need libffi-dev

The system need libffi-dev to allow pip to install
all dependencies.

Change-Id: Idc1a9cff79289b0ae391c4ab1ba4c3c483fb854a
Closes-Bug: 1286167
(cherry picked from commit 3b9066c54c14b59daca624fdb89f22a62fd1d8e8)
Merge "System need libffi-dev" into stable/havana