consistent error message formatting

Author: James Barnett

bin/snap-sync

@@ -45,7 +45,7 @@ while [[ $# -gt 0 ]]; do
             exit 1
         ;;
         *)
-            printf "Error: Unknown option: $key\n"
+            printf "ERROR: Unknown option: $key\n"
             printf "Run 'snap-sync -h' for valid options.\n"
             exit 1
         ;;
@@ -132,7 +132,7 @@ for x in $selected_configs; do
     if [[ -f "/etc/snapper/configs/$x" ]]; then
         source /etc/snapper/configs/$x
     else
-        printf "Error: Selected snapper configuration $x does not exist.\n"
+        printf "ERROR: Selected snapper configuration $x does not exist.\n"
         exit 1
     fi