chore: ignore F821 for python 2 compatible code

flake8 cannot auto detect `six.PY2` branch

Author: weakish

leancloud/engine/utils.py

@@ -21,7 +21,7 @@ def sign_by_key(timestamp, key):
 if six.PY2:
 
     def to_native(s):
-        if isinstance(s, unicode):
+        if isinstance(s, unicode):  # noqa: F821
             return s.encode("utf-8")
         return s
 

leancloud/file_.py

@@ -65,7 +65,7 @@ def __init__(self, name="", data=None, mime_type=None):
             data.seek(0, os.SEEK_SET)
         except Exception:
             if (six.PY3 and isinstance(data, (memoryview, bytes))) or (
-                six.PY2 and isinstance(data, (buffer, memoryview, str))
+                six.PY2 and isinstance(data, (buffer, memoryview, str))  # noqa: F821
             ):
                 data = io.BytesIO(data)
             elif data.read:

tests/test_file.py

@@ -48,7 +48,7 @@ def fn(s):
 
         fn(StringIO.StringIO(b))
         fn(cStringIO.StringIO(b))
-        fn(buffer(b))
+        fn(buffer(b))  # noqa: F821
 
 
 def test_create_with_url():  # type: () -> None