Handle invalid ssh exception

app/controllers/application_controller.rb

@@ -14,6 +14,10 @@ class ApplicationController < ActionController::Base
     render "errors/gitolite", layout: "error"
   end
 
+  rescue_from Gitlab::Gitolite::InvalidKey do |exception|
+    render "errors/invalid_ssh_key", layout: "error"
+  end
+
   rescue_from Encoding::CompatibilityError do |exception|
     render "errors/encoding", layout: "error", status: 404
   end

app/views/errors/invalid_ssh_key.html.haml

+%h1 Git Error
+%hr
+%p Seems like SSH Key you provided is not a valid SSH key.

lib/gitlab/backend/gitolite.rb

@@ -6,6 +6,7 @@ require 'fileutils'
 module Gitlab
   class Gitolite
     class AccessDenied < StandardError; end
+    class InvalidKey < StandardError; end
 
     def set_key key_id, key_content, projects
       configure do |c|
@@ -190,8 +191,12 @@ module Gitlab
         end
       end
     rescue Exception => ex
-      Gitlab::Logger.error(ex.message)
-      raise Gitolite::AccessDenied.new("gitolite timeout")
+      if ex.message =~ /is not a valid SSH key string/
+        raise Gitolite::InvalidKey.new("ssh key is not valid")
+      else
+        Gitlab::Logger.error(ex.message)
+        raise Gitolite::AccessDenied.new("gitolite timeout")
+      end
     end
   end
 end