Fixed #18196 -- Improved loaddata error messages.

django/core/management/commands/loaddata.py

@@ -196,6 +196,10 @@ def read(self):
                                     loaded_object_count += loaded_objects_in_fixture
                                     fixture_object_count += objects_in_fixture
                                     label_found = True
+                                except Exception as e:
+                                    if not isinstance(e, CommandError):
+                                        e.args = ("Problem installing fixture '%s': %s" % (full_path, e),)
+                                    raise
                                 finally:
                                     fixture.close()
 
@@ -209,16 +213,18 @@ def read(self):
             # Since we disabled constraint checks, we must manually check for
             # any invalid keys that might have been added
             table_names = [model._meta.db_table for model in models]
-            connection.check_constraints(table_names=table_names)
+            try:
+                connection.check_constraints(table_names=table_names)
+            except Exception as e:
+                e.args = ("Problem installing fixtures: %s" % e,)
+                raise
 
         except (SystemExit, KeyboardInterrupt):
             raise
         except Exception as e:
             if commit:
                 transaction.rollback(using=using)
                 transaction.leave_transaction_management(using=using)
-            if not isinstance(e, CommandError):
-                e.args = ("Problem installing fixture '%s': %s" % (full_path, e),)
             raise
 
         # If we found even one object in a fixture, we need to reset the

django/test/signals.py

@@ -4,7 +4,6 @@
 from django.conf import settings
 from django.db import connections
 from django.dispatch import receiver, Signal
-from django.template import context
 from django.utils import timezone
 
 template_rendered = Signal(providing_args=["template", "context"])
@@ -48,9 +47,17 @@ def update_connections_time_zone(**kwargs):
 @receiver(setting_changed)
 def clear_context_processors_cache(**kwargs):
     if kwargs['setting'] == 'TEMPLATE_CONTEXT_PROCESSORS':
+        from django.template import context
         context._standard_context_processors = None
 
 
+@receiver(setting_changed)
+def clear_serializers_cache(**kwargs):
+    if kwargs['setting'] == 'SERIALIZATION_MODULES':
+        from django.core import serializers
+        serializers._serializers = {}
+
+
 @receiver(setting_changed)
 def language_changed(**kwargs):
     if kwargs['setting'] in ('LOCALE_PATHS', 'LANGUAGE_CODE'):

tests/regressiontests/fixtures_regress/tests.py

@@ -126,6 +126,20 @@ def test_unknown_format(self):
                 commit=False,
             )
 
+    @override_settings(SERIALIZATION_MODULES={'unkn': 'unexistent.path'})
+    def test_unimportable_serializer(self):
+        """
+        Test that failing serializer import raises the proper error
+        """
+        with self.assertRaisesRegexp(ImportError,
+                "No module named unexistent.path"):
+            management.call_command(
+                'loaddata',
+                'bad_fixture1.unkn',
+                verbosity=0,
+                commit=False,
+            )
+
     def test_invalid_data(self):
         """
         Test for ticket #4371 -- Loading a fixture file with invalid data