In auth-krb4.c, in krb4_init(), we have:
        if ((fd = mkstemp(authctxt->krb4_ticket_file)) != -1) {

which tries to create a temporary file to hold kerberos tickets.  This file is
created some lines above by:
        snprintf(authctxt->krb4_ticket_file, MAXPATHLEN, "%s%u_%ld",
So, mkstemp() is passes something like "/tmp/tkt9036_6294", with no Xs at the end.

On a RedHat 8.0, mkstemp() will fail if the file template does not end with at
least 6 Xs.

To fix this, replace the mkstemp line with:

if ((fd = open(authctxt->krb4_ticket_file, O_RDWR|O_CREAT|O_EXCL, 0x600)) != -1) {