Fix: check: non-zero exit status when there's a warning

lib/keyringer/actions/check

@@ -27,3 +27,8 @@ source "$LIB" maintenance $* || exit 1
 
 # This should be done here:
 # TODO: Check canaries' timestamps, warning by mail if configured by user preferences.
+
+# Since this is the check action, it should exit whenever there's a warning
+if [ "$KEYRINGER_HAS_EXPIRING_KEYS" == "1" ]; then
+  exit 1
+fi

lib/keyringer/functions

@@ -766,6 +766,8 @@ function keyringer_check_expiration {
 
       if [[ "$ahead" -gt "$expiry" ]] && [ "$BASENAME" == "check" ]; then
         echo "Warning: subkey from $recipient will expire soon, on `date --date="@$expiry"`"
+
+        KEYRINGER_HAS_EXPIRING_KEYS="1"
       fi
     fi
   done