writers test: fix python2 linter errors

pkgs/build-support/writers/test.nix

@@ -49,9 +49,11 @@ let
     python2 = writePython2Bin "test_writers" { libraries = [ python2Packages.enum ]; } ''
       from enum import Enum
 
+
       class Test(Enum):
           a = "success"
 
+
       print Test.a
     '';
 
@@ -112,9 +114,11 @@ let
     python2 = writePython2 "test_python2" { libraries = [ python2Packages.enum ]; } ''
       from enum import Enum
 
+
       class Test(Enum):
           a = "success"
 
+
       print Test.a
     '';