A recent change prevented hosting service forms from loading posted form

data if the form wasn't used to submit that data. This prevented crashes

in some situations, and unwanted (but harmless) "This field is required"

errors in others.
Unfortunately, that fix broke bug tracker configuration, as it was

making determinations for both the repository and bug tracker forms

based solely on the submitted repository data. This meant that if you

were using a bug tracker from a different service, things would break.
We now make that determination per-form, based on the proper fields in

the posted form data, preventing this problem.
While working on this, a couple other problems related to the bug

tracker configuration was found and fixed.
First, the "Type" field for bug trackers was visible when loading a

repository that had the "Use hosting service's bug tracker" checkbox

checked. Toggling that checkbox off and back on would properly hide the

Type field. This was happening because the "fake" hosting service

support (used to help guide people to Power Pack for configuration) was

overriding a previous calculation for the visiblity of this field. Now,

instead of overriding that calculation, the code that's supposed to

calculate it is invoked for fake services.
Second, if a SCMTool is in the database but no longer installed, the

form would crash trying to import it. We now catch this, and just skip

the tool, allowing the equivalent fake tool entry (if any) to show up

instead.

Unit tests pass.
Manually tested:

Setting no bug tracker for a repository
Setting a custom bug tracker
Setting a hosting service bug tracker for the same service as the

  repository.
Setting a hosting service bug tracker for a different service from

  the repository.
Loading the form when an SCMTool is unavailable.
Testing visibility for the Bug Tracker Type field on initial loads

  (with and without the "Use hosting" checkbox checked) and after

  toggling it.