Render sso deactived/success templates

We switched from reading them directly from disk to making them
into jinja2.Template files, which broke stuff. We now render
them to turn them back into text.

Author: anoadragon453

synapse/config/sso.py

@@ -29,23 +29,30 @@ def read_config(self, config, **kwargs):
         # The sso-specific template_dir
         template_dir = sso_config.get("template_dir")
 
+        # Read templates from disk
         (
-            self.sso_account_deactivated_template,
-            self.sso_auth_success_template,
             self.sso_redirect_confirm_template,
             self.sso_auth_confirm_template,
             self.sso_error_template,
+            sso_account_deactivated_template,
+            sso_auth_success_template,
         ) = self.read_templates(
             [
-                "sso_account_deactivated.html",
-                "sso_auth_success.html",
                 "sso_redirect_confirm.html",
                 "sso_auth_confirm.html",
                 "sso_error.html",
+                "sso_account_deactivated.html",
+                "sso_auth_success.html",
             ],
             template_dir,
         )
 
+        # These templates have no placeholders, so render them here
+        self.sso_account_deactivated_template = (
+            sso_account_deactivated_template.render()
+        )
+        self.sso_auth_success_template = sso_auth_success_template.render()
+
         self.sso_client_whitelist = sso_config.get("client_whitelist") or []
 
         # Attempt to also whitelist the server's login fallback, since that fallback sets