Commit from Sugar Labs: Translation System by user cjl.: 407 of 407 messages translated (0 fuzzy).
Really include content bundles in bundle registry

It looks like I messed up with some rebasing and dropped a bit of
8148fdf96f58fa017e3a68dc7 before submitting.

These additional changes are needed for content bundles to actually be
indexed in the bundle registry, and hence subject to automatic updates.
Bundle registry tests

Requested during the review of automatic activity updates.
Fix pep8 errors

pep8 1.6.4 detects more issues