parent count warning message from cell.py prints multiple times

[7yl4r]

if I insert a cell with 0 parents the log will read something like:

2013-10-23 23:54:17,704 WARNING:n_parents=0 less than 3, using random dna for missing parents
2013-10-23 23:54:17,706 WARNING:n_parents=1 less than 3, using random dna for missing parents
2013-10-23 23:54:17,707 WARNING:n_parents=2 less than 3, using random dna for missing parents

Ideally only the first of these messages should show.