certbot: an empty change shouldn't raise an exception

CHANGELOG.md

@@ -23,6 +23,7 @@ The **patch** part changes incrementally at each release.
 
 ### Fixed
 
+* certbot: an empty change shouldn't raise an exception
 * certbot: fix "no-self-upgrade" option
 
 ### Removed

certbot/files/hooks/z-commit-etc.sh

@@ -22,7 +22,7 @@ main() {
           message="[letsencrypt] certificates renewal (${RENEWED_DOMAINS})"
           ${git_bin} commit --message "${message}" --quiet
       else
-          error "Weird, nothing has changed but the hook has been executed for '${RENEWED_DOMAINS}'"
+          debug "Weird, nothing has changed but the hook has been executed for '${RENEWED_DOMAINS}'"
       fi
     fi
 }