Fix suppressed exceptions for migration downgrade

In SQLAlchemy migration versions 009, 010 and 020, we missed
reraising exceptions while logging errors in case of a downgrade.
We don't want exceptions to pass silently. This patch fixes that.

Closes-bug: 1227881

Change-Id: Id11b1c5d2e26d208e88bb84e5b46c4b7affc3f9f
Merge "Fix suppressed exceptions for migration downgrade"