[utils.py] gathering/refactoring into a "utils/" folder (#6095)

* [utils] gathering/refactoring into a "utils/" folder

Moving current utils.py into utils/core.py and moving other *util*
modules under this new "utils/" as well.

Following steps include eroding at "utils/core.py" and breaking it down
into smaller modules.

* Improve tests

* Make loading examples in scope for tests

* Remove test class attrs examples_loaded and requires_examples

tests/base_tests.py

@@ -1,44 +1,29 @@
 """Unit tests for Superset"""
 import json
-import logging
-import os
 import unittest
 
 from flask_appbuilder.security.sqla import models as ab_models
 from mock import Mock
 import pandas as pd
 
-from superset import app, cli, db, security_manager
+from superset import app, db, security_manager
 from superset.connectors.druid.models import DruidCluster, DruidDatasource
 from superset.connectors.sqla.models import SqlaTable
 from superset.models import core as models
-from superset.utils import get_main_database
-
+from superset.utils.core import get_main_database
 
 BASE_DIR = app.config.get('BASE_DIR')
 
 
 class SupersetTestCase(unittest.TestCase):
-    requires_examples = False
-    examples_loaded = False
 
     def __init__(self, *args, **kwargs):
-        if (
-            self.requires_examples and
-            not os.environ.get('examples_loaded')
-        ):
-            logging.info('Loading examples')
-            cli.load_examples_run(load_test_data=True)
-            logging.info('Done loading examples')
-            security_manager.sync_role_definitions()
-            os.environ['examples_loaded'] = '1'
-        else:
-            security_manager.sync_role_definitions()
         super(SupersetTestCase, self).__init__(*args, **kwargs)
         self.client = app.test_client()
         self.maxDiff = None
 
-        cli.load_test_users_run()
+    @classmethod
+    def create_druid_test_objects(cls):
         # create druid cluster and druid datasources
         session = db.session
         cluster = (