Agreed, I think this is a good change and in line with how the check functions work in general.
> Instead of giving suggestion about updating the pg_database catalog, can we give "ALTER DATABASE <datname> ALLOW_CONNECTIONS true;" command?
I would actually prefer to not give any suggestions at all, we typically don't in these error messages. Since there are many ways to do it (dropping the database being one) I think leaving that to the user is per application style.
> Also, it would be good if we give 2 spaces after full stop in an error message.
Correct, fixed in the attached which also tweaks the language slightly to match other errors.
I propose to commit the attached, which also adds a function comment while there, unless there are objections.