Use webmock to stub external web requests.

spec/controllers/uploads_controller_spec.rb

@@ -74,7 +74,8 @@ describe UploadsController do
         controller.stubs(:is_api?).returns(true)
 
         Jobs.expects(:enqueue).with(:create_avatar_thumbnails, anything)
-        Excon.stub({ method: :head, hostname: 'example.com' }, {})
+
+        stub_request(:head, 'http://example.com/image.png')
         stub_request(:get, "http://example.com/image.png").to_return(body: File.read('spec/fixtures/images/logo.png'))
 
         xhr :post, :create, url: 'http://example.com/image.png', type: "avatar", synchronous: true

spec/controllers/user_avatars_controller_spec.rb

@@ -24,7 +24,6 @@ describe UserAvatarsController do
       SiteSetting.s3_upload_bucket = "test"
       SiteSetting.s3_cdn_url = "http://cdn.com"
 
-      Excon.stub({ method: :head, hostname: 'cdn.com' }, {})
       stub_request(:get, "http://cdn.com/something/else").to_return(body: 'image')
 
       GlobalSetting.expects(:cdn_url).returns("http://awesome.com/boom")