fix django import errors during xmodule_assets

xmodule_assets doesn't pass edx's django settings when it executes
resulting in an import error for xmodules that access django settings
directly or imports code that does.

Updated ProctorPanel to move all code that needs to read from django
settings into __init__. This includes the import of
django.contrib.auth.models.User which automatically tries to read from
django settings on load.

common/lib/xmodule/xmodule/proctor_module.py

@@ -6,7 +6,6 @@ from lxml import etree
 from pkg_resources import resource_string
 
 from django.conf import settings
-from django.contrib.auth.models import User
 
 from xmodule.x_module import XModule
 from xmodule.seq_module import SequenceDescriptor
@@ -32,14 +31,14 @@ class ProctorPanel(object):
 
     '''
 
-    ProctorPanelInterface = getattr(settings, 'PROCTOR_PANEL_INTERFACE', {})
-    ProctorPanelServer = ProctorPanelInterface.get('url', "")
 
     def __init__(self, user_id, procset_name):
-
+        self.ProctorPanelInterface = getattr(settings, 'PROCTOR_PANEL_INTERFACE', {})
+        self.ProctorPanelServer = self.ProctorPanelInterface.get('url', "")
         self.user_id = user_id
         self.procset_name = procset_name
         self.ses = requests.session()
+        from django.contrib.auth.models import User
         self.user = User.objects.get(pk=user_id)
 
     def is_released(self):