Fix `static_cache_control` deprecation warning

1. Fix the message by wrapping the value in missing quotes and adding
the missing backtick at the end. Finally, :lipstick: by adding a space
inside the curly braces.

Before:

`config.public_file_server.headers = {'Cache-Control' => public,
max-age=31536000}

Now:

`config.public_file_server.headers = { 'Cache-Control' => 'public,
max-age=31536000' }`

2. Display `static_cache_control` instead of static_cache_control. This
follows what the 2 neighboring methods are doing.

3. Use strip_heredoc to improve the code formatting and readability
like the 2 neighboring methods and wrap to 80 characters.

1 files changed, 6 insertions, 3 deletions

diff --git a/railties/lib/rails/application/configuration.rb b/railties/lib/rails/application/configuration.rb
index 7ac010b903..785671f70b 100644
--- a/railties/lib/rails/application/configuration.rb
+++ b/railties/lib/rails/application/configuration.rb
@@ -56,9 +56,12 @@ module Rails
       end
 
       def static_cache_control=(value)
-        ActiveSupport::Deprecation.warn("static_cache_control is deprecated and will be removed in Rails 5.1. " \
-                                        "Please use `config.public_file_server.headers = {'Cache-Control' => #{value}} " \
-                                        "instead.")
+        ActiveSupport::Deprecation.warn <<-eow.strip_heredoc
+          `static_cache_control` is deprecated and will be removed in Rails 5.1.
+          Please use
+          `config.public_file_server.headers = { 'Cache-Control' => '#{value}' }`
+          instead.
+        eow
 
         @static_cache_control = value
       end