Add a custom sagecell server URL option.

Author: drgrice1

conf/localOverrides.conf.dist

@@ -434,6 +434,19 @@ $mail{feedbackRecipients}    = [
 # use this setting when running Rserve in a docker container.
 #$pg{specialPGEnvironmentVars}{Rserve} = {host => "r"};
 
+################################################################################
+# Usa a custom Sage cell server.
+################################################################################
+
+# By default the AskSage method of PG uses the public sagecell service located
+# at https://sagecell.sagemath.org/service. However, the server at that address
+# is no longer accepting public requests. So in order for problems that use the
+# AskSage method to work a different sagecell server must be used.  Uncomment
+# the line below and set the value to a custom sagecell server address to use
+# with the AskSage method.
+
+#$pg{URLs}{sagecellService} = 'http://localhost:3500/service';
+
 ################################################################################
 # Authentication
 ################################################################################