feat: create anonymous user at runtime if it doesn't exist already.

related: #88

cubicweb/pyramid/core.py

@@ -386,8 +386,19 @@ def includeme(config):
     with repo.internal_cnx() as cnx:
         login = config.registry['cubicweb.config'].anonymous_user()[0]
         if login is not None:
-            config.registry['cubicweb.anonymous_eid'] = cnx.find(
-                'CWUser', login=login).one().eid
+            try:
+                config.registry['cubicweb.anonymous_eid'] = cnx.find(
+                    'CWUser', login=login).one().eid
+            except cubicweb.NoResultError:
+                # Anonymous access is enabled, but anonymous user doesn't exist
+                # which happens when we authorized anonymous access on a previously
+                # private instance.
+                from cubicweb.server import create_user
+                anonlogin, anonpwd = config.registry['cubicweb.config'].anonymous_user()
+                create_user(cnx, anonlogin, anonpwd, 'guests')
+                cnx.commit()
+                config.registry['cubicweb.anonymous_eid'] = cnx.find(
+                    'CWUser', login=login).one().eid
 
     config.add_request_method(
         _cw_session, name='cw_session', property=True, reify=True)