Prevent loading contextvars in python 3.6

Fixes: #6166
Change-Id: I1355e9a8b6455ca377892214e9426c8f70441f98

1 files changed, 12 insertions, 7 deletions

diff --git a/lib/sqlalchemy/util/_concurrency_py3k.py b/lib/sqlalchemy/util/_concurrency_py3k.py
index 94f4705d8..b905f903b 100644
--- a/lib/sqlalchemy/util/_concurrency_py3k.py
+++ b/lib/sqlalchemy/util/_concurrency_py3k.py
@@ -6,16 +6,21 @@ from typing import Coroutine
 
 import greenlet
 
+from . import compat
 from .. import exc
 
-try:
-    from contextvars import copy_context as _copy_context
 
-    # If greenlet.gr_context is present in current version of greenlet,
-    # it will be set with a copy of the current context on creation.
-    # Refs: https://github.com/python-greenlet/greenlet/pull/198
-    getattr(greenlet.greenlet, "gr_context")
-except (ImportError, AttributeError):
+if compat.py37:
+    try:
+        from contextvars import copy_context as _copy_context
+
+        # If greenlet.gr_context is present in current version of greenlet,
+        # it will be set with a copy of the current context on creation.
+        # Refs: https://github.com/python-greenlet/greenlet/pull/198
+        getattr(greenlet.greenlet, "gr_context")
+    except (ImportError, AttributeError):
+        _copy_context = None
+else:
     _copy_context = None