INCR-249: Make compatible with Python 3.x without breaking Python 2.7 support (#20528)

* INCR-249: Make compatible with Python 3.x without breaking Python 2.7 support --> openedx/core/djangoapps/content/block_structure

* INCR-249: Grouped six package

* INCR-249: Remove the duplicate lines for absolute_import

openedx/core/djangoapps/content/block_structure/admin.py

@@ -1,9 +1,11 @@
 """
 Django Admin for Block Structures.
 """
-from django.contrib import admin
+from __future__ import absolute_import
 
 from config_models.admin import ConfigurationModelAdmin
+from django.contrib import admin
+
 from .config.models import BlockStructureConfiguration
 
 

openedx/core/djangoapps/content/block_structure/api.py

@@ -1,7 +1,10 @@
 """
 Higher order functions built on the BlockStructureManager to interact with a django cache.
 """
+from __future__ import absolute_import
+
 from django.core.cache import cache
+
 from xmodule.modulestore.django import modulestore
 
 from .manager import BlockStructureManager

openedx/core/djangoapps/content/block_structure/apps.py

@@ -2,6 +2,8 @@
 Configuration for block_structure djangoapp
 """
 
+from __future__ import absolute_import
+
 from django.apps import AppConfig
 
 

openedx/core/djangoapps/content/block_structure/block_structure.py

@@ -8,15 +8,18 @@ The following internal data structures are implemented:
     _BlockRelations - Data structure for a single block's relations.
     _BlockData - Data structure for a single block's data.
 """
+from __future__ import absolute_import
+
 from copy import deepcopy
 from functools import partial
 from logging import getLogger
 
-from openedx.core.lib.graph_traversals import traverse_topologically, traverse_post_order
+import six
+
+from openedx.core.lib.graph_traversals import traverse_post_order, traverse_topologically
 
 from .exceptions import TransformerException
 
-
 logger = getLogger(__name__)  # pylint: disable=invalid-name
 
 
@@ -145,7 +148,7 @@ class BlockStructure(object):
             iterator(UsageKey) - An iterator of the usage
             keys of all the blocks in the block structure.
         """
-        return self._block_relations.iterkeys()
+        return six.iterkeys(self._block_relations)
 
     #--- Block structure traversal methods ---#
 
@@ -432,14 +435,14 @@ class BlockStructureBlockData(BlockStructure):
         Returns iterator of (UsageKey, BlockData) pairs for all
         blocks in the BlockStructure.
         """
-        return self._block_data_map.iteritems()
+        return six.iteritems(self._block_data_map)
 
     def itervalues(self):
         """
         Returns iterator of BlockData for all blocks in the
         BlockStructure.
         """
-        return self._block_data_map.itervalues()
+        return six.itervalues(self._block_data_map)
 
     def __getitem__(self, usage_key):
         """
@@ -835,7 +838,7 @@ class BlockStructureModulestoreData(BlockStructureBlockData):
         Iterates through all instantiated xBlocks that were added and
         collects all xBlock fields that were requested.
         """
-        for xblock_usage_key, xblock in self._xblock_map.iteritems():
+        for xblock_usage_key, xblock in six.iteritems(self._xblock_map):
             block_data = self._get_or_create_block(xblock_usage_key)
             for field_name in self._requested_xblock_fields:
                 self._set_xblock_field(block_data, xblock, field_name)

openedx/core/djangoapps/content/block_structure/config/__init__.py

@@ -9,7 +9,6 @@ from openedx.core.lib.cache_utils import request_cached
 
 from .models import BlockStructureConfiguration
 
-
 # Namespace
 WAFFLE_NAMESPACE = u'block_structure'
 

openedx/core/djangoapps/content/block_structure/config/models.py

@@ -3,8 +3,8 @@ Models for configuration of Block Structures.
 """
 from __future__ import absolute_import
 
-from django.db.models import IntegerField
 from config_models.models import ConfigurationModel
+from django.db.models import IntegerField
 
 
 class BlockStructureConfiguration(ConfigurationModel):

openedx/core/djangoapps/content/block_structure/factory.py

@@ -1,7 +1,7 @@
 """
 Module for factory class for BlockStructure objects.
 """
-from .block_structure import BlockStructureModulestoreData, BlockStructureBlockData
+from .block_structure import BlockStructureBlockData, BlockStructureModulestoreData
 
 
 class BlockStructureFactory(object):

openedx/core/djangoapps/content/block_structure/management/commands/generate_course_blocks.py

@@ -5,21 +5,21 @@ from __future__ import absolute_import
 
 import logging
 
+import six
 from django.core.management.base import BaseCommand
 import six
 from six import text_type
-from xmodule.modulestore.django import modulestore
 
 import openedx.core.djangoapps.content.block_structure.api as api
-from openedx.core.djangoapps.content.block_structure.config import STORAGE_BACKING_FOR_CACHE, waffle
-import openedx.core.djangoapps.content.block_structure.tasks as tasks
 import openedx.core.djangoapps.content.block_structure.store as store
+import openedx.core.djangoapps.content.block_structure.tasks as tasks
+from openedx.core.djangoapps.content.block_structure.config import STORAGE_BACKING_FOR_CACHE, waffle
 from openedx.core.lib.command_utils import (
     get_mutually_exclusive_required_option,
-    validate_dependent_option,
     parse_course_keys,
+    validate_dependent_option
 )
-
+from xmodule.modulestore.django import modulestore
 
 log = logging.getLogger(__name__)
 

openedx/core/djangoapps/content/block_structure/management/commands/tests/test_generate_course_blocks.py

@@ -3,20 +3,22 @@ Tests for generate_course_blocks management command.
 """
 from __future__ import absolute_import
 
+import itertools
+
 import ddt
 from django.core.management.base import CommandError
-import itertools
+from mock import patch
 import six
 from six.moves import range
-from mock import patch
 
-from xmodule.modulestore.tests.django_utils import ModuleStoreTestCase
-from xmodule.modulestore.tests.factories import CourseFactory
-from .. import generate_course_blocks
 from openedx.core.djangoapps.content.block_structure.tests.helpers import (
     is_course_in_block_structure_cache,
-    is_course_in_block_structure_storage,
+    is_course_in_block_structure_storage
 )
+from xmodule.modulestore.tests.django_utils import ModuleStoreTestCase
+from xmodule.modulestore.tests.factories import CourseFactory
+
+from .. import generate_course_blocks
 
 
 @ddt.ddt

openedx/core/djangoapps/content/block_structure/manager.py

@@ -2,10 +2,14 @@
 Top-level module for the Block Structure framework with a class for managing
 BlockStructures.
 """
+from __future__ import absolute_import
+
 from contextlib import contextmanager
 
+import six
+
 from . import config
-from .exceptions import UsageKeyNotInBlockStructure, TransformerDataIncompatible, BlockStructureNotFound
+from .exceptions import BlockStructureNotFound, TransformerDataIncompatible, UsageKeyNotInBlockStructure
 from .factory import BlockStructureFactory
 from .store import BlockStructureStore
 from .transformers import BlockStructureTransformers
@@ -69,8 +73,8 @@ class BlockStructureManager(object):
             if starting_block_usage_key not in block_structure:
                 raise UsageKeyNotInBlockStructure(
                     u"The requested usage_key '{0}' is not found in the block_structure with root '{1}'",
-                    unicode(starting_block_usage_key),
-                    unicode(self.root_block_usage_key),
+                    six.text_type(starting_block_usage_key),
+                    six.text_type(self.root_block_usage_key),
                 )
             block_structure.set_root_block(starting_block_usage_key)
         transformers.transform(block_structure)

openedx/core/djangoapps/content/block_structure/models.py

@@ -2,22 +2,26 @@
 Models used by the block structure framework.
 """
 
+from __future__ import absolute_import
+
 from contextlib import contextmanager
 from datetime import datetime
+from logging import getLogger
+
+import six
+from six.moves import map
 from django.conf import settings
 from django.core.exceptions import SuspiciousOperation
 from django.core.files.base import ContentFile
 from django.db import models, transaction
-from logging import getLogger
-
 from model_utils.models import TimeStampedModel
+
 from openedx.core.djangoapps.xmodule_django.models import UsageKeyWithRunField
 from openedx.core.storage import get_storage
 
 from . import config
 from .exceptions import BlockStructureNotFound
 
-
 log = getLogger(__name__)
 
 
@@ -35,7 +39,7 @@ def _directory_name(data_usage_key):
     """
     # replace any '/' in the usage key so they aren't interpreted
     # as folder separators.
-    encoded_usage_key = unicode(data_usage_key).replace('/', '_')
+    encoded_usage_key = six.text_type(data_usage_key).replace('/', '_')
     return '{}{}'.format(
         settings.BLOCK_STRUCTURES_SETTINGS.get('DIRECTORY_PREFIX', ''),
         encoded_usage_key,
@@ -219,7 +223,7 @@ class BlockStructureModel(TimeStampedModel):
         Returns a string representation of this model.
         """
         return u', '.join(
-            u'{}: {}'.format(field_name, unicode(getattr(self, field_name)))
+            u'{}: {}'.format(field_name, six.text_type(getattr(self, field_name)))
             for field_name in self.UNIQUENESS_FIELDS
         )
 
@@ -255,7 +259,7 @@ class BlockStructureModel(TimeStampedModel):
         Deletes the given files from storage.
         """
         storage = _bs_model_storage()
-        map(storage.delete, files)
+        list(map(storage.delete, files))
 
     @classmethod
     def _get_all_files(cls, data_usage_key):

openedx/core/djangoapps/content/block_structure/signals.py

@@ -1,13 +1,15 @@
 """
 Signal handlers for invalidating cached data.
 """
+from __future__ import absolute_import
+
+import six
 from django.conf import settings
 from django.dispatch.dispatcher import receiver
+from opaque_keys.edx.locator import LibraryLocator
 
 from xmodule.modulestore.django import SignalHandler
 
-from opaque_keys.edx.locator import LibraryLocator
-
 from . import config
 from .api import clear_course_from_cache
 from .tasks import update_course_in_cache_v2
@@ -27,7 +29,7 @@ def update_block_structure_on_course_publish(sender, course_key, **kwargs):  # p
         clear_course_from_cache(course_key)
 
     update_course_in_cache_v2.apply_async(
-        kwargs=dict(course_id=unicode(course_key)),
+        kwargs=dict(course_id=six.text_type(course_key)),
         countdown=settings.BLOCK_STRUCTURES_SETTINGS['COURSE_PUBLISH_TASK_DELAY'],
     )
 

openedx/core/djangoapps/content/block_structure/store.py

@@ -2,8 +2,12 @@
 Module for the Storage of BlockStructure objects.
 """
 # pylint: disable=protected-access
+from __future__ import absolute_import
+
 from logging import getLogger
 
+import six
+
 from openedx.core.lib.cache_utils import zpickle, zunpickle
 
 from . import config
@@ -13,7 +17,6 @@ from .factory import BlockStructureFactory
 from .models import BlockStructureModel
 from .transformer_registry import TransformerRegistry
 
-
 logger = getLogger(__name__)  # pylint: disable=C0103
 
 
@@ -27,7 +30,7 @@ class StubModel(object):
         self.data_usage_key = root_block_usage_key
 
     def __unicode__(self):
-        return unicode(self.data_usage_key)
+        return six.text_type(self.data_usage_key)
 
     def delete(self):
         """
@@ -217,12 +220,12 @@ class BlockStructureStore(object):
         BlockStructureModel or StubModel.
         """
         if _is_storage_backing_enabled():
-            return unicode(bs_model)
+            return six.text_type(bs_model)
 
         else:
             return "v{version}.root.key.{root_usage_key}".format(
-                version=unicode(BlockStructureBlockData.VERSION),
-                root_usage_key=unicode(bs_model.data_usage_key),
+                version=six.text_type(BlockStructureBlockData.VERSION),
+                root_usage_key=six.text_type(bs_model.data_usage_key),
             )
 
     @staticmethod
@@ -235,7 +238,7 @@ class BlockStructureStore(object):
             data_version=getattr(root_block, 'course_version', None),
             data_edit_timestamp=getattr(root_block, 'subtree_edited_on', None),
             transformers_schema_version=TransformerRegistry.get_write_version_hash(),
-            block_structure_schema_version=unicode(BlockStructureBlockData.VERSION),
+            block_structure_schema_version=six.text_type(BlockStructureBlockData.VERSION),
         )
 
     @staticmethod

openedx/core/djangoapps/content/block_structure/tasks.py

@@ -1,19 +1,20 @@
 """
 Asynchronous tasks related to the Course Blocks sub-application.
 """
+from __future__ import absolute_import
+
 import logging
 
-from capa.responsetypes import LoncapaProblemError
 from celery.task import task
 from django.conf import settings
-from lxml.etree import XMLSyntaxError
-
 from edxval.api import ValInternalError
+from lxml.etree import XMLSyntaxError
 from opaque_keys.edx.keys import CourseKey
 
-from xmodule.modulestore.exceptions import ItemNotFoundError
+from capa.responsetypes import LoncapaProblemError
 from openedx.core.djangoapps.content.block_structure import api
 from openedx.core.djangoapps.content.block_structure.config import STORAGE_BACKING_FOR_CACHE, waffle
+from xmodule.modulestore.exceptions import ItemNotFoundError
 
 log = logging.getLogger('edx.celery.task')
 

openedx/core/djangoapps/content/block_structure/transformer.py

@@ -2,6 +2,8 @@
 This module provides the abstract base class for all Block Structure
 Transformers.
 """
+from __future__ import absolute_import
+
 from abc import abstractmethod
 
 

openedx/core/djangoapps/content/block_structure/transformer_registry.py

@@ -2,11 +2,15 @@
 Block Structure Transformer Registry implemented using the platform's
 PluginManager.
 """
+from __future__ import absolute_import
+
 from base64 import b64encode
 from hashlib import sha1
 
-from openedx.core.lib.plugins import PluginManager
+import six
+
 from openedx.core.lib.cache_utils import process_cached
+from openedx.core.lib.plugins import PluginManager
 
 
 class TransformerRegistry(PluginManager):
@@ -30,7 +34,7 @@ class TransformerRegistry(PluginManager):
                 registered with the platform's PluginManager.
         """
         if cls.USE_PLUGIN_MANAGER:
-            return set(cls.get_available_plugins().itervalues())
+            return set(six.itervalues(cls.get_available_plugins()))
         else:
             return set()
 

openedx/core/djangoapps/content/block_structure/transformers.py

@@ -1,14 +1,15 @@
 """
 Module for a collection of BlockStructureTransformers.
 """
+from __future__ import absolute_import
+
 import functools
 from logging import getLogger
 
-from .exceptions import TransformerException, TransformerDataIncompatible
+from .exceptions import TransformerDataIncompatible, TransformerException
 from .transformer import FilteringTransformerMixin
 from .transformer_registry import TransformerRegistry
 
-
 logger = getLogger(__name__)  # pylint: disable=C0103