Move Model imports down into methods which use the models, since

Django 1.9 no longer allows model imports during app init.

cms/lib/xblock/tagging/tagging.py

@@ -11,7 +11,6 @@ from xmodule.capa_module import CapaModule
 from edxmako.shortcuts import render_to_string
 from django.conf import settings
 from webob import Response
-from .models import TagCategories
 
 
 _ = lambda text: text
@@ -29,6 +28,7 @@ class StructuredTagsAside(XBlockAside):
         """
         Return available tags
         """
+        from .models import TagCategories
         return TagCategories.objects.all()
 
     def _get_studio_resource_url(self, relative_url):

common/djangoapps/static_replace/__init__.py

@@ -5,9 +5,6 @@ from django.contrib.staticfiles.storage import staticfiles_storage
 from django.contrib.staticfiles import finders
 from django.conf import settings
 
-from static_replace.models import AssetBaseUrlConfig, AssetExcludedExtensionsConfig
-from xmodule.modulestore.django import modulestore
-from xmodule.modulestore import ModuleStoreEnum
 from xmodule.contentstore.content import StaticContent
 
 from opaque_keys.edx.locator import AssetLocator
@@ -177,6 +174,8 @@ def replace_static_urls(text, data_directory=None, course_id=None, static_asset_
             if exists_in_staticfiles_storage:
                 url = staticfiles_storage.url(rest)
             else:
+                # Import here because models can't be imported at top of module __init__.py.
+                from static_replace.models import AssetBaseUrlConfig, AssetExcludedExtensionsConfig
                 # if not, then assume it's courseware specific content and then look in the
                 # Mongo-backed database
                 base_url = AssetBaseUrlConfig.get_base_url()

common/djangoapps/xblock_django/user_service.py

 """
 Support for converting a django user to an XBlock user
 """
-from django.contrib.auth.models import User
 from opaque_keys.edx.keys import CourseKey
-from xblock.reference.user_service import XBlockUser, UserService
+from xblock.reference.user_service import UserService
 from student.models import anonymous_id_for_user, get_user_by_username_or_email
 
 ATTR_KEY_IS_AUTHENTICATED = 'edx-platform.is_authenticated'
@@ -43,6 +42,7 @@ class DjangoXBlockUserService(UserService):
         if not self.get_current_user().opt_attrs.get(ATTR_KEY_USER_IS_STAFF):
             return None
 
+        from django.contrib.auth.models import User
         try:
             user = get_user_by_username_or_email(username_or_email=username)
         except User.DoesNotExist:
@@ -55,6 +55,7 @@ class DjangoXBlockUserService(UserService):
         """
         A function that returns an XBlockUser from the current Django request.user
         """
+        from xblock.reference.user_service import XBlockUser
         xblock_user = XBlockUser(is_current_user=True)
 
         if django_user is not None and django_user.is_authenticated():

common/lib/xmodule/xmodule/modulestore/django.py

@@ -29,7 +29,6 @@ from xmodule.contentstore.django import contentstore
 from xmodule.modulestore.draft_and_published import BranchSettingMixin
 from xmodule.modulestore.mixed import MixedModuleStore
 from xmodule.util.django import get_current_request_hostname
-import xblock.reference.plugins
 
 try:
     # We may not always have the request_cache module available
@@ -39,20 +38,6 @@ try:
 except ImportError:
     HAS_REQUEST_CACHE = False
 
-# We also may not always have the current request user (crum) module available
-try:
-    from xblock_django.user_service import DjangoXBlockUserService
-    from crum import get_current_user
-
-    HAS_USER_SERVICE = True
-except ImportError:
-    HAS_USER_SERVICE = False
-
-try:
-    from xblock_django.models import XBlockDisableConfig
-except ImportError:
-    XBlockDisableConfig = None
-
 log = logging.getLogger(__name__)
 ASSET_IGNORE_REGEX = getattr(settings, "ASSET_IGNORE_REGEX", r"(^\._.*$)|(^\.DS_Store$)|(^.*~$)")
 
@@ -180,6 +165,15 @@ def create_modulestore_instance(
     if issubclass(class_, BranchSettingMixin):
         _options['branch_setting_func'] = _get_modulestore_branch_setting
 
+    # We also may not always have the current request user (crum) module available
+    try:
+        from xblock_django.user_service import DjangoXBlockUserService
+        from crum import get_current_user
+
+        HAS_USER_SERVICE = True
+    except ImportError:
+        HAS_USER_SERVICE = False
+
     if HAS_USER_SERVICE and not user_service:
         xb_user_service = DjangoXBlockUserService(get_current_user())
     else:
@@ -188,6 +182,11 @@ def create_modulestore_instance(
     if 'read_preference' in doc_store_config:
         doc_store_config['read_preference'] = getattr(ReadPreference, doc_store_config['read_preference'])
 
+    try:
+        from xblock_django.models import XBlockDisableConfig
+    except ImportError:
+        XBlockDisableConfig = None
+
     if XBlockDisableConfig and settings.FEATURES.get('ENABLE_DISABLING_XBLOCK_TYPES', False):
         disabled_xblock_types = XBlockDisableConfig.disabled_block_types()
     else:
@@ -195,6 +194,8 @@ def create_modulestore_instance(
 
     xblock_field_data_wrappers = [load_function(path) for path in settings.XBLOCK_FIELD_DATA_WRAPPERS]
 
+    import xblock.reference.plugins
+
     return class_(
         contentstore=content_store,
         metadata_inheritance_cache_subsystem=metadata_inheritance_cache,

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

@@ -5,8 +5,6 @@ from django.dispatch.dispatcher import receiver
 
 from xmodule.modulestore.django import SignalHandler
 
-from .models import CourseStructure
-
 
 @receiver(SignalHandler.course_published)
 def listen_for_course_publish(sender, course_key, **kwargs):  # pylint: disable=unused-argument
@@ -16,6 +14,8 @@ def listen_for_course_publish(sender, course_key, **kwargs):  # pylint: disable=
     # Import tasks here to avoid a circular import.
     from .tasks import update_course_structure
 
+    from .models import CourseStructure
+
     # Delete the existing discussion id map cache to avoid inconsistencies
     try:
         structure = CourseStructure.objects.get(course_id=course_key)