Escape changelog RST

[Joshua Harlow]

Some changelogs generated (and then included in say sphinx) can cause sphinx to error out when including the changelog.

It might be nice to escape rst-syntax in changelogs (so they can be included without issue) in generated docs.

For example: from oslo.versionedobjects changelog

    * Fixes up Bucket to throw proper NotFound and NotEmpty exceptions in constructor and delete() method, and fixes up objectstore_unittest to properly use assertRaises() to check for proper exceptions and remove the assert_ calls

This entry (which is just any other commit message) has a line for 'assert_'

When included via sphinx, this causes sphinx to try to find a reference to 'assert_'

When building:

```
reading sources... [ 70%] history
reading sources... [100%] usage
ChangeLog:1845: WARNING: Inline emphasis start-string without end-string.
ChangeLog:3167: ERROR: Unknown target name: "assert".
ChangeLog:3172: ERROR: Unknown target name: "assert".
looking for now-outdated files... none found

```

Instead if the changelog could support rst-escaping (optionally?) that would be super and avoid these types of errors/issues.

[Wes Turner (wes-turner)]

Here's a potential rst_escape function:

- https://github.com/westurner/dotfiles/blob/e866c630952/scripts/git-changelog.py

A separate package with a comprehensive test suite might be good.

Extracted, this function could be part of docutils?

[Stephen Finucane (stephenfinucane)]

This was fixed in pbr 3.0.0 [1].

[1] https://github.com/openstack-dev/pbr/commits/3cc5af104eef83ccca1e46cbc8089b479f3ddd0f