Fixed gis_tests.geoapp when run in isolation.

"from django.db.models import *" in contrib/gis/db/models/__init__.py could
obscure gis's functions.py resulting in exceptions like:
"module 'django.db.models.functions' has no attribute 'Union'".

django/contrib/gis/db/models/__init__.py

@@ -1,8 +1,17 @@
 from django.db.models import *  # NOQA isort:skip
+from django.db.models import __all__ as models_all  # isort:skip
 from django.contrib.gis.db.models.aggregates import *  # NOQA
-from django.contrib.gis.db.models.fields import (  # NOQA
+from django.contrib.gis.db.models.aggregates import __all__ as aggregates_all
+from django.contrib.gis.db.models.fields import (
     GeometryCollectionField, GeometryField, LineStringField,
     MultiLineStringField, MultiPointField, MultiPolygonField, PointField,
     PolygonField, RasterField,
 )
-from django.contrib.gis.db.models.manager import GeoManager  # NOQA
+from django.contrib.gis.db.models.manager import GeoManager
+
+__all__ = models_all + aggregates_all
+__all__ += [
+    'GeometryCollectionField', 'GeometryField', 'LineStringField',
+    'MultiLineStringField', 'MultiPointField', 'MultiPolygonField', 'PointField',
+    'PolygonField', 'RasterField', 'GeoManager',
+]

django/db/models/__init__.py

@@ -1,25 +1,28 @@
-from django.core.exceptions import ObjectDoesNotExist  # NOQA
-from django.db.models import signals  # NOQA
+from django.core.exceptions import ObjectDoesNotExist
+from django.db.models import signals
 from django.db.models.aggregates import *  # NOQA
-from django.db.models.deletion import (  # NOQA
+from django.db.models.aggregates import __all__ as aggregates_all
+from django.db.models.deletion import (
     CASCADE, DO_NOTHING, PROTECT, SET, SET_DEFAULT, SET_NULL, ProtectedError,
 )
-from django.db.models.expressions import (  # NOQA
+from django.db.models.expressions import (
     Case, Expression, ExpressionWrapper, F, Func, Value, When,
 )
 from django.db.models.fields import *  # NOQA
-from django.db.models.fields.files import FileField, ImageField  # NOQA
-from django.db.models.fields.proxy import OrderWrt  # NOQA
+from django.db.models.fields import __all__ as fields_all
+from django.db.models.fields.files import FileField, ImageField
+from django.db.models.fields.proxy import OrderWrt
 from django.db.models.indexes import *  # NOQA
-from django.db.models.lookups import Lookup, Transform  # NOQA
-from django.db.models.manager import Manager  # NOQA
-from django.db.models.query import (  # NOQA
+from django.db.models.indexes import __all__ as indexes_all
+from django.db.models.lookups import Lookup, Transform
+from django.db.models.manager import Manager
+from django.db.models.query import (
     Prefetch, Q, QuerySet, prefetch_related_objects,
 )
 
 # Imports that would create circular imports if sorted
-from django.db.models.base import DEFERRED, Model  # NOQA isort:skip
-from django.db.models.fields.related import (  # NOQA isort:skip
+from django.db.models.base import DEFERRED, Model  # isort:skip
+from django.db.models.fields.related import (  # isort:skip
     ForeignKey, ForeignObject, OneToOneField, ManyToManyField,
     ManyToOneRel, ManyToManyRel, OneToOneRel,
 )
@@ -52,3 +55,16 @@ def permalink(func):
         bits = func(*args, **kwargs)
         return reverse(bits[0], None, *bits[1:3])
     return inner
+
+
+__all__ = aggregates_all + fields_all + indexes_all
+__all__ += [
+    'ObjectDoesNotExist', 'signals',
+    'CASCADE', 'DO_NOTHING', 'PROTECT', 'SET', 'SET_DEFAULT', 'SET_NULL',
+    'ProtectedError',
+    'Case', 'Expression', 'ExpressionWrapper', 'F', 'Func', 'Value', 'When',
+    'FileField', 'ImageField', 'OrderWrt', 'Lookup', 'Transform', 'Manager',
+    'Prefetch', 'Q', 'QuerySet', 'prefetch_related_objects', 'DEFERRED', 'Model',
+    'ForeignKey', 'ForeignObject', 'OneToOneField', 'ManyToManyField',
+    'ManyToOneRel', 'ManyToManyRel', 'OneToOneRel', 'permalink',
+]

django/db/models/indexes.py

@@ -4,7 +4,7 @@ import hashlib
 
 from django.utils.encoding import force_bytes
 
-__all__ = ['Index']
+__all__ = [str('Index')]
 
 # The max length of the names of the indexes (restricted to 30 due to Oracle)
 MAX_NAME_LENGTH = 30