Code review comment for lp:~danilo/launchpad/bug-480652

= Bug 480652 =

Fix an OOPS in trying to link to a default series branch (translations are imported from) if it's not set, yet imports are requested. It OOPSes only if translations bzr export is set at the same time.

Some drive-by test cleanups as well.

= Tests =

bin/test -vvct productseries-translations.txt

= Demo & QA =

1. create a "Hosted" branch for "evolution" export: https://code.launchpad.dev/evolution/+addbranch
2. go to https://translations.launchpad.dev/evolution/trunk/+translations-settings and set export branch to the above created branch (use "~username/evolution/name" to set it)
3. go to https://code.launchpad.dev/evolution/trunk/+linkbranch and remove the branch reference
4. https://translations.launchpad.dev/evolution/trunk/ doesn't OOPS with the fix, OOPSes without

= Launchpad lint =

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

Linting changed files:
  lib/lp/translations/browser/productseries.py
  lib/lp/translations/stories/productseries/xx-productseries-translations-settings.txt
  lib/lp/translations/stories/standalone/xx-productseries-translations.txt