Coding error detected, it must be fixed by a programmer: Context passed must be course context.

More information about this error

Debug info:
Error code: codingerror
Stack trace:
line 115 of /lib/classes/event/course_viewed.php: coding_exception thrown
line 252 of /lib/classes/event/base.php: call to core\event\course_viewed->validate_data()
line 308 of /course/view.php: call to core\event\base::create()

This first came to light by behat tests as illustrated by the following fail:

(::) failed steps (::)

01. Moodle exception: Coding error detected, it must be fixed by a programmer: Context passed must be course context. More information about this error

    Debug info:

    Error code: codingerror

    Stack trace:

    line 115 of /lib/classes/event/course_viewed.php: coding_exception thrown

    line 252 of /lib/classes/event/base.php: call to core\event\course_viewed->validate_data()

    line 289 of /course/view.php: call to core\event\base::create()

    In step `And I press "Save changes"'.                                                     # behat_forms::press_button()

    From scenario `Restore a backup into a new course changing the course format afterwards'. # /var/www/integration/backup/util/ui/tests/behat/restore_moodle2_courses.feature:82

    Of feature `Restore Moodle 2 course backups'.

After a bit of research I find that it is in fact because of the social course format, looking at https://github.com/samhemelryk/moodle/blob/master/course/view.php#L286 before this line $context is instance of context_course.
After this line $context is instance of context_module.

Now it appears to me that the course format should not change $context (a downside to executing format code in the global scope).
However I wonder if it is also a flaw of the logging code. I would bet that social isn't the only format that does this nasty. Perhaps we need to double check the context before instantiating the event data.