ERR_print_errors() is a convenience function that prints the error
strings for all errors that OpenSSL has recorded to bp, thus
emptying the error queue.
ERR_print_errors_fp() is the same, except that the output goes to a
The error strings will have the following format:
[pid]:error:[error code]:[library name]:[function name]:[reason string]:[file name]:[line]:[optional text message]
error code is an 8 digit hexadecimal number. library name,
function name and reason string are ASCII text, as is optional
text message if one was set for the respective error code.
If there is no text string registered for the given error code,
the error string will contain the numeric code.