Code review comment for lp:~salgado/launchpad/bug-433991

= Summary =

Make sure zope.i18nmessageid.message.Message get interpolated when
building a page's title.

== Proposed fix ==

The new fmt:pagetitle formatter iterates over the breadcrumbs and join
their text in a single string, but the leaf breadcrumb may have Message
objects (from the view's .page_title) as their text, so when they're
joined they are not interpolated and we end up with things like 'Ask a
question about ${context}' in the title.

== Tests ==

./bin/test -vvm canonical.launchpad -t test_breadcrumbs

== Demo and Q/A ==

https://answers.launchpad.dev/ubuntu/+source/mozilla-firefox/+addquestion

= Launchpad lint =

Checking for conflicts. and issues in doctests and templates.
Running jslint, xmllint, pyflakes, and pylint.
Using normal rules.

Linting changed files:
  lib/canonical/launchpad/webapp/tests/test_breadcrumbs.py
  lib/canonical/launchpad/browser/launchpad.py