Fixed flake8 warnings.

tests/custom_lookups/tests.py

@@ -37,6 +37,7 @@ class Div3Transform(models.Transform):
         lhs, lhs_params = qn.compile(self.lhs)
         return 'mod(%s, 3)' % lhs, lhs_params
 
+
 class Div3BilateralTransform(Div3Transform):
     bilateral = True
 
@@ -49,6 +50,7 @@ class Mult3BilateralTransform(models.Transform):
         lhs, lhs_params = qn.compile(self.lhs)
         return '3 * (%s)' % lhs, lhs_params
 
+
 class UpperBilateralTransform(models.Transform):
     bilateral = True
     lookup_name = 'upper'