how to concatenate python quantities?

Question

I am working with the quantities module of python, and I want to concatenate two quantiy arrays. If I use numpy.concatenate(), I loose the unit from quantities. The quantities package itself does not provide a .concatenate() method for its arrays. How to avoid this?

Example:

import scipy as sp
import quantities as pq
a = [1,2,3]*pq.V
b = [4,5,6]*pq.V
sp.concatenate([a,b])

returns

array([1., 2., 3., 4., 5., 6.]) * dimensionless