Fix a crash in the course participants page for unenrolled users

The participant details page may be opened for users that are not
enrolled in the course. The code `enrollment.status` used to crash
when `enrollment` is `None`.

exercise/staff_views.py

@@ -230,15 +230,20 @@ def get_resource_objects(self):
     def get_common_objects(self):
         profile = self.student.userprofile
         enrollment = self.instance.get_enrollment_for(profile.user)
-        if enrollment.status != Enrollment.ENROLLMENT_STATUS.ACTIVE:
+        if not enrollment:
+            messages.warning(self.request, _("USER_NOT_ENROLLED"))
+        elif enrollment.status != Enrollment.ENROLLMENT_STATUS.ACTIVE:
             status_string = Enrollment.ENROLLMENT_STATUS[enrollment.status]
             messages.warning(
                 self.request,
                 format_lazy(
                     _("NO_LONGER_PARTICIPATING_IN_COURSE -- {status}"),
                     status=status_string
                 ),
-            ),
+            )
+        elif enrollment.role in (Enrollment.ENROLLMENT_ROLE.TEACHER, Enrollment.ENROLLMENT_ROLE.ASSISTANT):
+            messages.warning(self.request, _("USER_IS_COURSE_STAFF"))
+
         exercise = LearningObject.objects.find_enrollment_exercise(
             self.instance,
             profile

locale/en/LC_MESSAGES/django.po

@@ -6,7 +6,7 @@ msgid ""
 msgstr ""
 "Project-Id-Version: PACKAGE VERSION\n"
 "Report-Msgid-Bugs-To: \n"
-"POT-Creation-Date: 2021-09-13 16:29+0300\n"
+"POT-Creation-Date: 2021-09-14 16:14+0300\n"
 "PO-Revision-Date: 2021-05-27 14:47+0300\n"
 "Last-Translator: Ella Anttila <[email protected]>\n"
 "Language-Team: English<>\n"
@@ -2839,12 +2839,20 @@ msgstr "The review was saved successfully and the submitters were notified."
 msgid "ERROR_FAILED_TO_LOAD_RESOURCE"
 msgstr "Failed to load the resource."
 
+#: exercise/staff_views.py
+msgid "USER_NOT_ENROLLED"
+msgstr "This person is not enrolled in the course."
+
 #: exercise/staff_views.py
 #, python-brace-format
 msgid "NO_LONGER_PARTICIPATING_IN_COURSE -- {status}"
 msgstr ""
 "This student is no longer participating in the course (status: {status})."
 
+#: exercise/staff_views.py
+msgid "USER_IS_COURSE_STAFF"
+msgstr "This person is a member of the course staff."
+
 #: exercise/staff_views.py
 #, python-brace-format
 msgid "ERROR_INVALID_POST_DATA -- {error}"

locale/fi/LC_MESSAGES/django.po

@@ -6,7 +6,7 @@ msgid ""
 msgstr ""
 "Project-Id-Version: \n"
 "Report-Msgid-Bugs-To: \n"
-"POT-Creation-Date: 2021-09-13 16:29+0300\n"
+"POT-Creation-Date: 2021-09-14 16:14+0300\n"
 "PO-Revision-Date: 2019-08-14 12:16+0200\n"
 "Last-Translator: Ella Anttila <[email protected]>\n"
 "Language-Team: Finnish <>\n"
@@ -2842,11 +2842,19 @@ msgstr "Palaute on tallennettu, ja opiskelijoille on lähetetty ilmoitus."
 msgid "ERROR_FAILED_TO_LOAD_RESOURCE"
 msgstr "Lataus epäonnistui."
 
+#: exercise/staff_views.py
+msgid "USER_NOT_ENROLLED"
+msgstr "Tämä henkilö ei ole ilmoittautunut kurssille."
+
 #: exercise/staff_views.py
 #, python-brace-format
 msgid "NO_LONGER_PARTICIPATING_IN_COURSE -- {status}"
 msgstr "Tämä opiskelija ei enää osallistu kurssille (tila: {status})."
 
+#: exercise/staff_views.py
+msgid "USER_IS_COURSE_STAFF"
+msgstr "Tämä henkilö kuuluu kurssin henkilökuntaan."
+
 #: exercise/staff_views.py
 #, python-brace-format
 msgid "ERROR_INVALID_POST_DATA -- {error}"