Add Allen to py3 and lcg slots
See lhcb/Allen!396 (closed) where @dcampora suggests testing Allen in a python3 build slot.
Whilst I was there, also add Allen to the LCG slots (in preparation for when it is a Moore dependency).
See lhcb/Allen!396 (closed) where @dcampora suggests testing Allen in a python3 build slot.
Whilst I was there, also add Allen to the LCG slots (in preparation for when it is a Moore dependency).