python: Convert more percent formatting to Python 3.6 f-strings.

Generated by pyupgrade --py36-plus.

Now including %d, %i, %u, and multi-line strings.

Signed-off-by: Anders Kaseorg <anders@zulip.com>

zproject/prod_settings_template.py

@@ -223,7 +223,7 @@ SOCIAL_AUTH_SAML_ORG_INFO = {
     "en-US": {
         "displayname": "Example, Inc. Zulip",
         "name": "zulip",
-        "url": "%s%s" % ('https://', EXTERNAL_HOST),
+        "url": "{}{}".format('https://', EXTERNAL_HOST),
     },
 }
 SOCIAL_AUTH_SAML_ENABLED_IDPS = {

zproject/test_extra_settings.py

@@ -206,7 +206,7 @@ SOCIAL_AUTH_SAML_ORG_INFO = {
     "en-US": {
         "name": "example",
         "displayname": "Example Inc.",
-        "url": "%s%s" % ('http://', EXTERNAL_HOST),
+        "url": "{}{}".format('http://', EXTERNAL_HOST),
     },
 }