fix NameError

lib/mastodon/version.rb

@@ -17,7 +17,15 @@ module Mastodon
     end
 
     def default_prerelease
-      'rc1'
+      'rc2'
+    end
+
+       def prerelease
+      ENV['MASTODON_VERSION_PRERELEASE'].presence || default_prerelease
+    end
+
+    def build_metadata
+      ['glitch', ENV.fetch('MASTODON_VERSION_METADATA', nil)].compact_blank.join('.')
     end
 
     def suffix