Display more clean error on users.json/sites.json load error

src/Site/SiteManager.py

@@ -33,7 +33,13 @@ class SiteManager(object):
         address_found = []
         added = 0
         # Load new adresses
-        for address, settings in json.load(open("%s/sites.json" % config.data_dir)).items():
+        try:
+            json_path = "%s/sites.json" % config.data_dir
+            data = json.load(open(json_path))
+        except Exception as err:
+            raise Exception("Unable to load %s: %s" % (json_path, err))
+
+        for address, settings in data.items():
             if address not in self.sites:
                 if os.path.isfile("%s/%s/content.json" % (config.data_dir, address)):
                     # Root content.json exists, try load site

src/User/UserManager.py

@@ -24,7 +24,13 @@ class UserManager(object):
         added = 0
         s = time.time()
         # Load new users
-        for master_address, data in list(json.load(open("%s/users.json" % config.data_dir)).items()):
+        try:
+            json_path = "%s/users.json" % config.data_dir
+            data = json.load(open(json_path))
+        except Exception as err:
+            raise Exception("Unable to load %s: %s" % (json_path, err))
+
+        for master_address, data in list(data.items()):
             if master_address not in self.users:
                 user = User(master_address, data=data)
                 self.users[master_address] = user