I´m having a weird problem. It won´t let me DROP the database because there´s someone else in it, hah.
mario_database=> DROP DATABASE second_database;
ERROR: database “second_database” is being accessed by other users
DETAIL: There is 1 other session using the database.
I am not sure which dbms you are using for this exercise but maybe try adding “with (force)” to the drop command or lookup a similar option for your dbms.