[SourcesManager] Move const_missing override to its own module

lib/cocoapods/sources_manager.rb

@@ -155,35 +155,31 @@ module Pod
   end
 
   # @!visibility private
+  module SourcesManagerMissingConstant
     SOURCES_MANAGER_CONSTANT_WARNINGS = Set.new
 
-  # @!visibility private
-  #
     # Warn about deprecated use of `Pod::SourcesManager` and return the config's
     # Source::Manager
     #
     # @return [Pod::Source::Manager]
     #
-  def self.sources_manager_constant
-    calling_line = caller[1]
-    if SOURCES_MANAGER_CONSTANT_WARNINGS.add?(calling_line)
+    def const_missing(const)
+      unless const.to_sym == :SourcesManager &&
+          ancestors.any? { |a| a == ::Pod || a.name.start_with?('Pod::') }
+        return super
+      end
+
+      calling_line = caller.first
+      if Pod::SourcesManagerMissingConstant::SOURCES_MANAGER_CONSTANT_WARNINGS.add?(calling_line)
         warn 'Usage of the constant `Pod::SourcesManager` is deprecated, ' \
              'use `Pod::Config.instance.sources_manager` instead ' \
              "(called from #{calling_line})"
       end
+
       Config.instance.sources_manager
     end
-end
-
-def Pod.const_missing(const)
-  return super unless const.to_sym == :SourcesManager
-  ::Pod.sources_manager_constant
-end
-
-def Object.const_missing(const)
-  unless const.to_sym == :SourcesManager &&
-      ancestors.any? { |a| a == ::Pod || a.name.start_with?('Pod::') }
-    return super
   end
-  ::Pod.sources_manager_constant
+
+  extend SourcesManagerMissingConstant
+  ::Object.send(:extend, SourcesManagerMissingConstant)
 end