Password protect a CodeIgniter subdirectory using .htpasswd, avoid 404 errors

.htaccess

#Using CPanel to password protect a CodeIgniter subdirectory, and getting a 404 error when trying to access the subdirectory? I got u fam.
# This goes in the .htaccess file in the directory you wish to protect
#The critical line is ErrorDocument 401 "Authorisation Required"

#----------------------------------------------------------------cp:ppd
# Section managed by cPanel: Password Protected Directories     -cp:ppd
# - Do not edit this section of the htaccess file!              -cp:ppd
#----------------------------------------------------------------cp:ppd
AuthType Basic
AuthName "My extremely secret directory"
AuthUserFile "/path/to/.htpasswd"
Require valid-user
#----------------------------------------------------------------cp:ppd
# End section managed by cPanel: Password Protected Directories -cp:ppd
#----------------------------------------------------------------cp:ppd

#Fixes your 404 issue
ErrorDocument 401 "Authorisation Required"

Credit where due: https://stackoverflow.com/a/38075858