Merge branch 'master' into bug/christina/studio

Conflicts:
	cms/djangoapps/contentstore/views.py
	common/lib/xmodule/xmodule/capa_module.py
	common/lib/xmodule/xmodule/combined_open_ended_module.py
	common/lib/xmodule/xmodule/peer_grading_module.py

common/lib/xmodule/xmodule/capa_module.py

@@ -9,7 +9,8 @@ import sys
 from pkg_resources import resource_string
 
 from capa.capa_problem import LoncapaProblem
-from capa.responsetypes import StudentInputError
+from capa.responsetypes import StudentInputError,\
+    ResponseError, LoncapaProblemError
 from capa.util import convert_files_to_filenames
 from .progress import Progress
 from xmodule.x_module import XModule

common/lib/xmodule/xmodule/peer_grading_module.py

@@ -12,6 +12,7 @@ from xmodule.modulestore.django import modulestore
 from .timeinfo import TimeInfo
 from xblock.core import Object, Integer, Boolean, String, Scope
 from xmodule.open_ended_grading_classes.xblock_field_types import StringyFloat
+from xmodule.fields import Date
 
 from xmodule.open_ended_grading_classes.peer_grading_service import PeerGradingService, GradingServiceError, MockPeerGradingService