Make change set comment rate limit errors display properly

Fixes #4320

app/assets/javascripts/index/changeset.js

@@ -47,7 +47,7 @@ OSM.Changeset = function (map) {
         OSM.loadSidebarContent(window.location.pathname, page.load);
       },
       error: function (xhr, xhr_status, http_status) {
-        $(form).find("#comment-error").text(http_status);
+        $(form).find("#comment-error").text(xhr.responseText);
         $(form).find("#comment-error").prop("hidden", false);
         $(form).find("input[type=submit]").prop("disabled", false);
       }

app/views/browse/changeset.html.erb

@@ -78,7 +78,7 @@
         <div class="mb-3">
           <textarea class="form-control" name="text" cols="40" rows="5"></textarea>
         </div>
-        <div id="comment-error" class="alert-danger p-2 mb-3" hidden>
+        <div id="comment-error" class="alert alert-danger p-2 mb-3" hidden>
         </div>
         <div>
           <input type="submit" name="comment" value="<%= t("javascripts.changesets.show.comment") %>" data-changeset-id="<%= @changeset.id %>" data-method="POST" data-url="<%= changeset_comment_url(@changeset) %>" disabled="1" class="btn btn-sm btn-primary" />

lib/osm.rb

@@ -355,6 +355,10 @@ module OSM
 
   # Raised when a rate limit is exceeded
   class APIRateLimitExceeded < APIError
+    def initialize
+      super "Rate limit exceeded"
+    end
+
     def status
       :too_many_requests
     end