Fix python3.x scoping issues with removed 'de' variable

In python3.x the 'de' variable will be removed from the
scope after the except block exits (if it ever is entered)
so we need to use a different variable name to ensure that
it will not be deleted so we can use it later.

This avoids errors of the format:

UnboundLocalError: local variable 'de' referenced before
                   assignment

Change-Id: I9ea2bd6b3a8c392f8d27b0130dd6b7683fc44e7c

1 files changed, 7 insertions, 3 deletions

diff --git a/oslo/db/sqlalchemy/session.py b/oslo/db/sqlalchemy/session.py
index b24e06b..04644b5 100644
--- a/oslo/db/sqlalchemy/session.py
+++ b/oslo/db/sqlalchemy/session.py
@@ -569,7 +569,10 @@ def _test_connection(engine, max_retries, retry_interval):
         attempts = itertools.count()
     else:
         attempts = six.moves.range(max_retries)
-    de = None
+    # See: http://legacy.python.org/dev/peps/pep-3110/#semantic-changes for
+    # why we are not using 'de' directly (it can be removed from the local
+    # scope).
+    de_ref = None
     for attempt in attempts:
         try:
             return exc_filters.handle_connect_error(engine)
@@ -577,9 +580,10 @@ def _test_connection(engine, max_retries, retry_interval):
             msg = _LW('SQL connection failed. %s attempts left.')
             LOG.warning(msg, max_retries - attempt)
             time.sleep(retry_interval)
+            de_ref = de
     else:
-        if de is not None:
-            six.reraise(type(de), de)
+        if de_ref is not None:
+            six.reraise(type(de_ref), de_ref)
 
 
 class Query(sqlalchemy.orm.query.Query):