Added a feature flag for add_srs_entry support; refs #22632 and #23504.

django/contrib/gis/db/backends/base.py

@@ -16,6 +16,9 @@ class BaseSpatialFeatures(object):
     # Does the database contain a SpatialRefSys model to store SRID information?
     has_spatialrefsys_table = True
 
+    # Does the backend support the django.contrib.gis.utils.add_srs_entry() utility?
+    supports_add_srs_entry = True
+
     # Reference implementation of 3D functions is:
     # http://postgis.net/docs/PostGIS_Special_Functions_Index.html#PostGIS_3D_Functions
     supports_3d_functions = False

django/contrib/gis/db/backends/mysql/base.py

@@ -10,6 +10,7 @@ from django.contrib.gis.db.backends.mysql.operations import MySQLOperations
 
 class DatabaseFeatures(BaseSpatialFeatures, MySQLDatabaseFeatures):
     has_spatialrefsys_table = False
+    supports_add_srs_entry = False
     supports_distances_lookups = False
     supports_transform = False
     supports_real_shape_operations = False

django/contrib/gis/db/backends/oracle/base.py

@@ -9,7 +9,7 @@ from django.contrib.gis.db.backends.oracle.operations import OracleOperations
 
 
 class DatabaseFeatures(BaseSpatialFeatures, OracleDatabaseFeatures):
-    pass
+    supports_add_srs_entry = False
 
 
 class DatabaseWrapper(OracleDatabaseWrapper):

django/contrib/gis/tests/test_spatialrefsys.py

@@ -105,6 +105,7 @@ class SpatialRefSysTest(unittest.TestCase):
             for i in range(3):
                 self.assertAlmostEqual(ellps1[i], ellps2[i], prec[i])
 
+    @skipUnlessDBFeature('supports_add_srs_entry')
     def test_add_entry(self):
         """
         Test adding a new entry in the SpatialRefSys model using the

django/contrib/gis/utils/srs.py

@@ -39,9 +39,8 @@ def add_srs_entry(srs, auth_name='EPSG', auth_srid=None, ref_sys_name=None,
     if not hasattr(connection.ops, 'spatial_version'):
         raise Exception('The `add_srs_entry` utility only works '
                         'with spatial backends.')
-    if connection.ops.oracle or connection.ops.mysql:
-        raise Exception('This utility does not support the '
-                        'Oracle or MySQL spatial backends.')
+    if not connection.features.supports_add_srs_entry:
+        raise Exception('This utility does not support your database backend.')
     SpatialRefSys = connection.ops.spatial_ref_sys()
 
     # If argument is not a `SpatialReference` instance, use it as parameter