Update pycountry code to new 1.19 backwards incompatible changes.

mayan/apps/documents/settings.py

@@ -9,8 +9,9 @@ from smart_settings import Namespace
 # TODO: Findout method to make languages names' translatable.
 # YAML fails to serialize ugettext_lazy and ugettext is not allowed at this
 # level
+
 LANGUAGE_CHOICES = [
-    (i.terminology, i.name) for i in list(pycountry.languages)
+    (i.iso639_3_code, i.name) for i in list(pycountry.languages)
 ]
 
 namespace = Namespace(name='documents', label=_('Documents'))