Mention optional requirement in docs

docs/install.rst

@@ -26,6 +26,8 @@ PyGtk
     http://www.pygtk.org/
 south
     http://south.aeracode.org/
+libravatar (optional for federated avatar support)
+    https://pypi.python.org/pypi/pyLibravatar
 Database backend
     Any database supported in Django will work, check their documentation for more details.
 

trans/admin_views.py

@@ -27,6 +27,7 @@ from django.utils.translation import ugettext as _
 from django.contrib import messages
 from django.conf import settings
 from weblate import appsettings
+from trans.util import HAS_LIBRAVATAR
 import weblate
 
 import os
@@ -112,6 +113,11 @@ def performance(request):
         ),
         'production-email',
     ))
+    checks.append((
+        _('Federated avatar support'),
+        HAS_LIBRAVATAR,
+        'production-avatar',
+    ))
     return render_to_response(
         "admin/performance.html",
         RequestContext(