Fix the regex for setting topic
Fix the regex for setting topic

The regex did not support the use of a `:` and a `#` in the bug
identification line. The updated regex now will support bug
identification lines that look like `Closes-Bug: #12345`.

Co-Authored-By: Nicolas Simonds <f27183276cbdd968cb09d16c8e66a12d1e4e9e4b@metacloud.com>
Change-Id: Ie5edd9a04fe714302f06b2df2c4c134a2ef2316a

openstack-infra/git-review,entropia1/git-review,ka2m/git-review