When making an error in the deps language, the error message tends to refer to extra parentheses if the field looks like a list of atoms.

For example, this file: (N.B. this is an error, the actual syntax is (glob_files *.txt))

(alias
 (name a)
 (deps (glob *.txt))
)

Displays the following error:

File "dune", line 3, characters 7-19:
These parentheses are no longer necessary with dune, please remove them.