[1.10.x] Fixed #27567 -- Fixed crash in the debug view when request.user errors.

Backport of 373140b07aa452946ccb6d5b0317fa09ed5bbdc2 from master

3 files changed, 45 insertions, 5 deletions

diff --git a/django/views/debug.py b/django/views/debug.py
index 1bcaaf8169..0ed55fdfe4 100644
--- a/django/views/debug.py
+++ b/django/views/debug.py
@@ -11,7 +11,7 @@ from django.template.defaultfilters import force_escape, pprint
 from django.urls import Resolver404, resolve
 from django.utils import lru_cache, six, timezone
 from django.utils.datastructures import MultiValueDict
-from django.utils.encoding import force_bytes, smart_text
+from django.utils.encoding import force_bytes, force_text, smart_text
 from django.utils.module_loading import import_string
 from django.utils.translation import ugettext as _
 
@@ -285,12 +285,24 @@ class ExceptionReporter(object):
                     'ascii', errors='replace'
                 )
         from django import get_version
+
+        if self.request is None:
+            user_str = None
+        else:
+            try:
+                user_str = force_text(self.request.user)
+            except Exception:
+                # request.user may raise OperationalError if the database is
+                # unavailable, for example.
+                user_str = '[unable to retrieve the current user]'
+
         c = {
             'is_email': self.is_email,
             'unicode_hint': unicode_hint,
             'frames': frames,
             'request': self.request,
             'filtered_POST': self.filter.get_post_parameters(self.request),
+            'user_str': user_str,
             'settings': get_safe_settings(),
             'sys_executable': sys.executable,
             'sys_version_info': '%d.%d.%d' % sys.version_info[0:3],
@@ -898,9 +910,9 @@ Exception Value: {{ exception_value|force_escape }}
   <h2>Request information</h2>
 
 {% if request %}
-  {% if request.user %}
+  {% if user_str %}
     <h3 id="user-info">USER</h3>
-    <p>{{ request.user }}</p>
+    <p>{{ user_str }}</p>
   {% endif %}
 
   <h3 id="get-info">GET</h3>
@@ -1099,7 +1111,7 @@ File "{{ frame.filename }}" in {{ frame.function }}
 {% if exception_type %}Exception Type: {{ exception_type }}{% if request %} at {{ request.path_info }}{% endif %}
 {% if exception_value %}Exception Value: {{ exception_value }}{% endif %}{% endif %}{% endif %}
 {% if request %}Request information:
-{% if request.user %}USER: {{ request.user }}{% endif %}
+{% if user_str %}USER: {{ user_str }}{% endif %}
 
 GET:{% for k, v in request.GET.items %}
 {{ k }} = {{ v|stringformat:"r" }}{% empty %} No GET data{% endfor %}
diff --git a/docs/releases/1.10.5.txt b/docs/releases/1.10.5.txt
index 18827e24a4..ac9270c3c0 100644
--- a/docs/releases/1.10.5.txt
+++ b/docs/releases/1.10.5.txt
@@ -9,4 +9,5 @@ Django 1.10.5 fixes several bugs in 1.10.4.
 Bugfixes
 ========
 
-* ...
+* Fixed a crash in the debug view if ``request.user`` can't be retrieved, such
+  as if the database is unavailable (:ticket:`27567`).
diff --git a/tests/view_tests/tests/test_debug.py b/tests/view_tests/tests/test_debug.py
index 714723c957..66796c705e 100644
--- a/tests/view_tests/tests/test_debug.py
+++ b/tests/view_tests/tests/test_debug.py
@@ -464,6 +464,33 @@ class ExceptionReporterTests(SimpleTestCase):
         html = reporter.get_traceback_html()
         self.assertIn("http://evil.com/", html)
 
+    def test_exception_fetching_user(self):
+        """
+        The error page can be rendered if the current user can't be retrieved
+        (such as when the database is unavailable).
+        """
+        class ExceptionUser(object):
+            def __str__(self):
+                raise Exception()
+
+        request = self.rf.get('/test_view/')
+        request.user = ExceptionUser()
+
+        try:
+            raise ValueError('Oops')
+        except ValueError:
+            exc_type, exc_value, tb = sys.exc_info()
+
+        reporter = ExceptionReporter(request, exc_type, exc_value, tb)
+        html = reporter.get_traceback_html()
+        self.assertIn('<h1>ValueError at /test_view/</h1>', html)
+        self.assertIn('<pre class="exception_value">Oops</pre>', html)
+        self.assertIn('<h3 id="user-info">USER</h3>', html)
+        self.assertIn('<p>[unable to retrieve the current user]</p>', html)
+
+        text = reporter.get_traceback_text()
+        self.assertIn('USER: [unable to retrieve the current user]', text)
+
 
 class PlainTextReportTests(SimpleTestCase):
     rf = RequestFactory()