Like the auth backends, the registration step isn't something that needs to be sandboxed (especially since you added try/except blocks around the built-in fields). Look for code that calls get_review_request_fieldsets, get_review_request_fields, or any other methods of iterating over the registered fields and fieldsets. For instance, the for_review_request_fieldset template tag will iterate over all the registered fieldset classes and instantiate them. That instantiation could fail if an extension author had a bug, which would end up making all the review request pages unusable.

Because the fields are third-party, this should be wrapped too.

Should wrap this.

Can you put the dictionary items on their own lines?

This should indicate the class name:

logging.error('Error instantiating ReviewRequestfieldSet %r: %s',
              field_cls, e, exc_info=1)

This should include the class name as above.

This should include the class name as above.

Almost. What I want looks more like this:

context = Context({
    'review_request_details': review,
    'request': request,
})

The text here still isn't great-- "fieldset_cls" is just an implementation detail of this method. It should read something like "Error instantiating ReviewRequestFieldset %r: %s"

This looks good. I'm going to hold off on pushing it because we're frozen for release.