Description of problem:
Manpage of selabel_media (selabel_lookup() function with MEDIA backend) states "Should there not be a valid entry in the media file, then the default removable_context file will be read (see removable_context(5)).", but it does not work. When I create a custom contexts file with no valid entry and supply it through SELABEL_OPT_PATH to selabel_open, selabel_lookup then produces error instead of returning default removable_context.

Version-Release number of selected component (if applicable):
libselinux-2.5-6.el7.x86_64

Steps to Reproduce:
$ cat > bug.c <<EOF
#include <stdio.h>
#include <selinux/selinux.h>
#include <selinux/label.h>

char *custom_contexts_file = "my_contexts";

int main (int argc, char **argv)
{
    struct selabel_handle *hnd = NULL;
    security_context_t selabel_context;
    struct selinux_opt selabel_option [] = { { SELABEL_OPT_PATH, custom_contexts_file } };

    if ((hnd = selabel_open(SELABEL_CTX_MEDIA, selabel_option, 4)) == NULL) {
        perror("selabel_open - ERROR");
        return 1;
    }

    if (selabel_lookup(hnd, &selabel_context, "floppy", 0) == -1) {
        perror("selabel_lookup - ERROR");
        selabel_close(hnd);
        return 1;
    }

    printf("%s\n", selabel_context);

    freecon(selabel_context);
    selabel_close(hnd);
    return 0;
}
EOF
$ gcc bug.c -o bug -lselinux
$ cat > my_contexts <<EOF
some_invalid_entry
EOF
$

Actual results:
$ ./bug
selabel_lookup - ERROR: No such file or directory
$

Expected results:
$ ./bug
system_u:object_r:removable_device_t:s0
$
(should match /etc/selinux/targeted/contexts/removable_context)

Additional info:
The other option is that the manpage is out of date and should be updated.