Fix CellDatabases fixture swallowing exceptions

The _wrap_target_cell() helper in the CellDatabases fixture was
accidentally changing the behavior of the target_cell() functionality
that it wraps by swallowing any exceptions raised and always returning
None. That was not intentional, and introduced by copying the exception
handler below a special case and returning None in a finally: context.

This just removes that exception handler to allow it to propagate to
the caller (as it would in production code), but returns (the
intended special case) if nothing is raised.

This also fixes a bit of the instance_list module that was working around
this quirk so that the code is more natural.

Change-Id: Id611678f53a2ad023dd336e30e62d5c3ae9ffd6e

1 files changed, 3 insertions, 5 deletions

diff --git a/nova/tests/fixtures.py b/nova/tests/fixtures.py
index a63c20287e..1be06f1ac4 100644
--- a/nova/tests/fixtures.py
+++ b/nova/tests/fixtures.py
@@ -419,11 +419,9 @@ class CellDatabases(fixtures.Fixture):
                 # cell_mapping of None. Since we're controlling our
                 # own targeting in this fixture, we need to call this out
                 # specifically and avoid switching global database state
-                try:
-                    with self._real_target_cell(context, cell_mapping) as c:
-                        yield c
-                finally:
-                    return
+                with self._real_target_cell(context, cell_mapping) as c:
+                    yield c
+                return
             ctxt_mgr = self._ctxt_mgrs[cell_mapping.database_connection]
             # This assumes the next local DB access is the same cell that
             # was targeted last time.