tests: load schema2 fixture only one time (#38067)

Use special db fixture (using pytest-django primitives and
transaction.atomic()) to initialize bijoe visualization only one time
for all tests on the schema2 fixture. It improves tests run time.

tests/conftest.py

@@ -1,7 +1,7 @@
 import os
 import glob
 import json
-from contextlib import closing
+from contextlib import closing, contextmanager
 import subprocess
 import tempfile
 import shutil
@@ -13,7 +13,7 @@ import django_webtest
 import psycopg2
 
 
-from django.db import connection
+from django.db import transaction
 from django.contrib.auth.models import User
 from django.core.management import call_command
 
@@ -49,6 +49,7 @@ def admin(db):
 SCHEMA_PATHS = os.path.join(os.path.dirname(__file__), 'fixtures/')
 
 
+@contextmanager
 def load_schema_db(schema):
     import random
 
@@ -107,8 +108,8 @@ def load_schema_db(schema):
 
 @pytest.fixture(scope='module')
 def schema1_db():
-    for x in load_schema_db('schema1'):
-        yield x
+    with load_schema_db('schema1') as d:
+        yield d
 
 
 @pytest.fixture
@@ -121,13 +122,23 @@ def schema1(db, schema1_db, settings):
 
 @pytest.fixture(scope='module')
 def schema2_db():
-    for x in load_schema_db('schema2'):
-        yield x
+    with load_schema_db('schema2') as d:
+        yield d
+
+
+@pytest.fixture(scope='module')
+def schema2_fixtures(schema2_db, django_db_setup, django_db_blocker):
+    with django_db_blocker.unblock():
+        with transaction.atomic():
+            try:
+                for json_fixture in schema2_db['fixtures']:
+                    call_command('loaddata', json_fixture)
+                yield
+            finally:
+                transaction.set_rollback(True)
 
 
 @pytest.fixture
-def schema2(db, schema2_db, settings):
+def schema2(schema2_db, schema2_fixtures, settings, django_db_blocker):
     settings.BIJOE_SCHEMAS = schema2_db['bijoe_schemas']
-    for json_fixture in schema2_db['fixtures']:
-        call_command('loaddata', json_fixture)
-    return schema2_db
+    yield schema2_db