There are several key load functions that all simply report the following in src/usr.bin/ssh/key.c:

debug("%s: %s", __func__, ssh_err(r));

or

error("%s: %s", __func__, ssh_err(r));

That's very vague, especially for an error message.

I'm specifically referring to the following functions.

key_load_cert()
key_load_public()
key_load_private()
key_load_private_cert()
key_load_private_type()

Unless there is a reason to not include this, I would find it very desirable to at least include the file that has the exception being reported in the debug or error message.