Merge pull request #5029 from certbot/issue_4792

expand nginx no name error

certbot-nginx/certbot_nginx/configurator.py

@@ -236,7 +236,11 @@ class NginxConfigurator(common.Plugin):
         if not vhost:
             # No matches. Raise a misconfiguration error.
             raise errors.MisconfigurationError(
-                        "Cannot find a VirtualHost matching domain %s." % (target_name))
+                        ("Cannot find a VirtualHost matching domain %s. "
+                         "In order for Certbot to correctly perform the challenge "
+                         "please add a corresponding server_name directive to your "
+                         "nginx configuration: "
+                         "https://nginx.org/en/docs/http/server_names.html") % (target_name))
         else:
             # Note: if we are enhancing with ocsp, vhost should already be ssl.
             if not vhost.ssl: