mkarchiso: check if the code signing files specified with option -c exist

Look for the files in `*_validate_options` and error out early if they do
not exist.

1 files changed, 1 insertions, 0 deletions

diff --git a/CHANGELOG.rst b/CHANGELOG.rst
index 4fa88db..400628a 100644
--- a/CHANGELOG.rst
+++ b/CHANGELOG.rst
@@ -15,6 +15,7 @@ Changed
 - Check if the GPG public key file was successfully placed in the work directory before trying to use it.
 - Open the file descriptors for code signing certificates and GPG public key as read only. Nothing from the within the
   ``pacstrap`` invoked chroot should ever be allowed to write outside of it.
+- Error out early if any of the code signing certificate files passed with option ``-c`` do not exist.
 
 Removed
 -------