raise ImproperlyConfigured error when settings have the wrong type

rest_framework/exceptions.py

@@ -146,6 +146,3 @@ class Throttled(APIException):
                 self.extra_detail % {'wait': self.wait}
             )
 
-
-class RESTFrameworkSettingHasUnexpectedClassWarning(Warning):
-    pass

rest_framework/settings.py

@@ -19,11 +19,10 @@ back to the defaults.
 """
 from __future__ import unicode_literals
 from collections import Iterable
-import warnings
+from django.core.exceptions import ImproperlyConfigured
 from django.conf import settings
 from django.utils import importlib, six
 from rest_framework import ISO_8601
-from rest_framework.exceptions import RESTFrameworkSettingHasUnexpectedClassWarning
 
 
 USER_SETTINGS = getattr(settings, 'REST_FRAMEWORK', None)
@@ -197,17 +196,14 @@ class APISettings(object):
             if issubclass(val.__class__, Iterable) \
                     and (not issubclass(default.__class__, Iterable)
                          or isinstance(val, six.string_types)):
-                warnings.warn(
-                    "The `{attr}` setting must be iterable".format(**locals()),
-                    RESTFrameworkSettingHasUnexpectedClassWarning,
-                    stacklevel=3
+                raise ImproperlyConfigured(
+                    'The "{attr}" setting must be a list or a tuple'
+                    .format(attr=attr)
                 )
             elif isinstance(default, six.string_types) and not \
                     isinstance(val, six.string_types):
-                warnings.warn(
-                    "The `{attr}` setting must be a string".format(**locals()),
-                    RESTFrameworkSettingHasUnexpectedClassWarning,
-                    stacklevel=3
+                raise ImproperlyConfigured(
+                    'The "{attr}" setting must be a string'.format(attr=attr)
                 )
 
         # Coerce import strings into classes

tests/test_settings.py

@@ -1,8 +1,8 @@
 from __future__ import unicode_literals
+from django.core.exceptions import ImproperlyConfigured
+import pytest
 import warnings
 from django.test import TestCase
-from rest_framework.exceptions import \
-    RESTFrameworkSettingHasUnexpectedClassWarning
 from rest_framework.settings import APISettings
 
 
@@ -21,37 +21,35 @@ class TestSettings(TestCase):
 
     def test_bad_iterable_setting_class_raises_warning(self):
         """
-        Make sure warnings are emitted when settings which should be iterable
-        are not.
+        Make sure errors are raised when settings which should be iterable are
+        not.
         """
         settings = APISettings({
             'DEFAULT_RENDERER_CLASSES': 'rest_framework.renderers.JSONRenderer'
         })
 
-        with warnings.catch_warnings(record=True) as w:
-            # Trigger a warning.
+        # Trigger the exception
+        with pytest.raises(ImproperlyConfigured) as exc_info:
             settings.DEFAULT_RENDERER_CLASSES
-            # Verify that a warning is thrown
-            assert len(w) == 1
-            assert issubclass(
-                w[-1].category, RESTFrameworkSettingHasUnexpectedClassWarning
-            )
+        expected_error = (
+            u'The "DEFAULT_RENDERER_CLASSES" setting must be a list or a tuple'
+        )
+        assert exc_info.value[0] == expected_error
 
     def test_bad_string_setting_class_raises_warning(self):
         """
-        Make sure warnings are emitted when settings which should be strings are
+        Make sure errors are raised when settings which should be strings are
         not.
         """
         settings = APISettings({
             'DEFAULT_METADATA_CLASS': []
         })
 
-        with warnings.catch_warnings(record=True) as w:
-            # Trigger a warning.
+        # Trigger the exception
+        with pytest.raises(ImproperlyConfigured) as exc_info:
             settings.DEFAULT_METADATA_CLASS
 
-            # Verify that a warning is thrown
-            assert len(w) == 1
-            assert issubclass(
-                w[-1].category, RESTFrameworkSettingHasUnexpectedClassWarning
-            )
+        expected_error = (
+            u'The "DEFAULT_METADATA_CLASS" setting must be a string'
+        )
+        assert exc_info.value[0] == expected_error