command -v nonexistent should exit 127

[floam]

When the -v or -V options are specified, the following exit values shall be returned:

0 Successful completion.
>0 The command_name could not be found or an error occurred.

Otherwise, the following exit values shall be returned:
126 The utility specified by command_name was found but could not be invoked.
127 An error occurred in the command utility or the utility specified by command_name could not be found.
Otherwise, the exit status of command shall be that of the simple command specified by the arguments to command.