Wrong error message for binary_to_existing_atom/2

[josevalim]

Describe the bug

If you give an ASCII binary to binary_to_existing_atom/1 and binary_to_existing_atom/2, which is not an existing atom, it raises as expected, but the error message says it says the error is caused by the utf8 encoding, which is wrong.

To Reproduce

3> binary_to_existing_atom(<<"oops doesnt_really_exist">>, utf8).
** exception error: bad argument
     in function  binary_to_existing_atom/2
        called as binary_to_existing_atom(<<"oops doesnt_really_exist">>,utf8)
        *** argument 1: invalid UTF8 encoding

Expected behavior

Probably to show the same error message as list_to_existing_atom/1:

7> list_to_existing_atom("oops doesnt_really_exist").
** exception error: bad argument
     in function  list_to_existing_atom/1
        called as list_to_existing_atom("oops doesnt_really_exist")
        *** argument 1: not an already existing atom

However, note that giving a non-list argument to list_to_existing_atom/1 shows a wrong error message too:

8> list_to_existing_atom(1).
** exception error: bad argument
     in function  list_to_existing_atom/1
        called as list_to_existing_atom(1)
        *** argument 1: not an already existing atom

It should say it is not a list instead.

Affected versions

OTP 24.