Does not load site_user during db upgrade

Fixes #2029 by ensuring we do not attempt to load site_user during a db
upgrade.  This is a workaround because loading the site_user will fail
because of a failed user change.  Should also avoid the problem in
future.

ckan/lib/cli.py

@@ -89,7 +89,7 @@ def _get_config(self):
         fileConfig(self.filename)
         return appconfig('config:' + self.filename)
 
-    def _load_config(self):
+    def _load_config(self, load_site_user=True):
         conf = self._get_config()
         assert 'ckan' not in dir() # otherwise loggers would be disabled
         # We have now loaded the config. Now we can import ckan for the
@@ -103,7 +103,7 @@ def _load_config(self):
         self.translator_obj = MockTranslator()
         self.registry.register(pylons.translator, self.translator_obj)
 
-        if model.user_table.exists():
+        if model.user_table.exists() and load_site_user:
             # If the DB has already been initialized, create and register
             # a pylons context object, and add the site user to it, so the
             # auth works as in a normal web request
@@ -153,11 +153,12 @@ class ManageDb(CkanCommand):
     min_args = 1
 
     def command(self):
-        self._load_config()
+        cmd = self.args[0]
+
+        self._load_config(cmd!='upgrade')
         import ckan.model as model
         import ckan.lib.search as search
 
-        cmd = self.args[0]
         if cmd == 'init':
 
             model.repo.init_db()