I try to drop a tablespace with dependent objects but get below error

SQL> !oerr ora 02449
02449, 00000, "unique/primary keys in table referenced by foreign keys"
// *Cause: An attempt was made to drop a table with unique or
//         primary keys referenced by foreign keys in another table.
// *Action: Before performing the above operations the table, drop the
//          foreign key constraints in other tables. You can see what
//          constraints are referencing a table by issuing the following
//          command:
//          SELECT * FROM USER_CONSTRAINTS WHERE TABLE_NAME = "tabnam";

Solution:

include cascade constraints option to drop the dependent objects!