Fix pep8

python/dune/perftool/sumfact/permutation.py

@@ -5,6 +5,7 @@ import itertools
 from dune.perftool.options import get_option
 from dune.perftool.sumfact.switch import get_facedir, get_facemod
 
+
 def sumfact_permutation_heuristic(permutations, stage):
     """Heuristic to choose a permutation