The @requires_user_profile decorator was added back when modern avatar

support was added, and one of its capabilities was to decorate a class

in order to decorate all test methods within.
This didn't actually work. Any class using this decorator would fail to

have its tests run. This was due to the initial check to determine if

this was decorating a function or a class by checking the result of

callable(...). Since unit test classes are callable, this passed. It

would then break running the test suite, which would cause the test

runner to ignore the class entirely.
We now check if it's a class directly instead, invoking the

class-specific logic for the first time. That logic unfortunately didn't

work, as it was trying to modify an immutable dictionary. This change

also fixes that, using setattr() instead.

Verified that the unit tests that weren't running before do run now.