More correct block size computation to ensure that all the models are computed...

More correct block size computation to ensure that all the models are computed and that each block contains all the redshifts for a given model.

pcigale/managers/parameters.py

@@ -72,8 +72,8 @@ class ParametersManagerGrid(object):
             Number of redshifts.
 
         """
-        k, m = divmod(len(l), nb)
-        step = k + nz - m
+        k = len(l) // nb
+        step = k + nz - k%nz
 
         return [l[i * step: (i+1) * step] for i in range(nb)]