fix flake8 errors

Author: zingale

mesh/array_indexer.py

@@ -111,7 +111,6 @@ def norm(self, n=0):
             return np.sqrt(self.g.dx * self.g.dy *
                            np.sum((_tmp[self.g.ilo:self.g.ihi+1, self.g.jlo:self.g.jhi+1]**2).flat))
 
-
     def copy(self):
         """make a copy of the array, defined on the same grid"""
         return ArrayIndexer(np.asarray(self).copy(), grid=self.g)

mesh/patch.py

@@ -675,7 +675,6 @@ def __init__(self, grid, idir, dtype=np.float64):
     def add_derived(self, func):
         raise NotImplementedError("derived variables not yet supported for face-centered data")
 
-
     def create(self):
         """Called after all the variables are registered and allocates the
         storage for the state data.  For face-centered data, we have