Improve clarity of error message for missing includes and eager_load

relations

activerecord/lib/active_record/associations/join_dependency.rb

@@ -228,7 +228,7 @@ def walk(left, right)
 
       def find_reflection(klass, name)
         klass._reflect_on_association(name) or
-          raise ConfigurationError, "Association named '#{ name }' was not found on #{ klass.name }; perhaps you misspelled it?"
+          raise ConfigurationError, "Can't join '#{ klass.name }' to association named '#{ name }'; perhaps you misspelled it?"
       end
 
       def build(associations, base_klass)

activerecord/test/cases/associations/join_model_test.rb

@@ -740,6 +740,23 @@ def test_has_many_with_pluralize_table_names_false
     assert_equal aircraft.engines, [engine]
   end
 
+  def test_proper_error_message_for_eager_load_and_includes_association_errors
+    includes_error = assert_raises(ActiveRecord::ConfigurationError) {
+      Post.includes(:nonexistent_relation).where(nonexistent_relation: {name: 'Rochester'}).find(1)
+    }
+    assert_equal("Can't join 'Post' to association named 'nonexistent_relation'; perhaps you misspelled it?", includes_error.message)
+
+    eager_load_error = assert_raises(ActiveRecord::ConfigurationError) {
+      Post.eager_load(:nonexistent_relation).where(nonexistent_relation: {name: 'Rochester'}).find(1)
+    }
+    assert_equal("Can't join 'Post' to association named 'nonexistent_relation'; perhaps you misspelled it?", eager_load_error.message)
+
+    includes_and_eager_load_error = assert_raises(ActiveRecord::ConfigurationError) {
+      Post.eager_load(:nonexistent_relation).includes(:nonexistent_relation).where(nonexistent_relation: {name: 'Rochester'}).find(1)
+    }
+    assert_equal("Can't join 'Post' to association named 'nonexistent_relation'; perhaps you misspelled it?", includes_and_eager_load_error.message)
+  end
+
   private
     # create dynamic Post models to allow different dependency options
     def find_post_with_dependency(post_id, association, association_name, dependency)