Only import from review_queue when it is installed

Author: gavinwahl

widgy/contrib/widgy_mezzanine/admin.py

@@ -24,14 +24,20 @@
 from widgy.forms import WidgyFormMixin, VersionedWidgyWidget
 from widgy.contrib.widgy_mezzanine import get_widgypage_model
 from widgy.contrib.widgy_mezzanine.views import ClonePageView, UnpublishView
-from widgy.contrib.review_queue.site import ReviewedWidgySite
 from widgy.utils import format_html
 from widgy.db.fields import get_site
 
 
 WidgyPage = get_widgypage_model()
 
 
+if 'widgy.contrib.review_queue' in settings.INSTALLED_APPS:
+    REVIEW_QUEUE_INSTALLED = True
+    from widgy.contrib.review_queue.site import ReviewedWidgySite
+else:
+    REVIEW_QUEUE_INSTALLED = False
+
+
 class PageVersionedWidgyWidget(VersionedWidgyWidget):
     template_name = 'widgy/widgy_mezzanine/versioned_widgy_field.html'
 
@@ -173,7 +179,7 @@ def render_change_form(self, request, context, add=False, change=False, form_url
 
     @property
     def has_review_queue(self):
-        return isinstance(self.get_site(), ReviewedWidgySite)
+        return REVIEW_QUEUE_INSTALLED and isinstance(self.get_site(), ReviewedWidgySite)
 
     def get_site(self):
         return get_site(settings.WIDGY_MEZZANINE_SITE)
@@ -293,7 +299,8 @@ def publish_page_on_approve(sender, instance, created, **kwargs):
                 status=CONTENT_STATUS_DRAFT,
             )
 
-if 'widgy.contrib.review_queue' in settings.INSTALLED_APPS:
+
+if REVIEW_QUEUE_INSTALLED:
     from widgy.contrib.review_queue.admin import VersionCommitAdminBase
     from widgy.contrib.review_queue.models import ReviewedVersionCommit