pep8: put pytest skip marker after imports

borg/testsuite/convert.py

@@ -10,8 +10,6 @@ try:
     import attic.helpers
 except ImportError:
     attic = None
-pytestmark = pytest.mark.skipif(attic is None,
-                                reason='cannot find an attic install')
 
 from ..converter import AtticRepositoryConverter, AtticKeyfileKey
 from ..helpers import get_keys_dir
@@ -19,6 +17,9 @@ from ..key import KeyfileKey
 from ..repository import Repository, MAGIC
 from . import BaseTestCase
 
+pytestmark = pytest.mark.skipif(attic is None,
+                                reason='cannot find an attic install')
+
 
 class ConversionTestCase(BaseTestCase):