Weird error in Emacs

init.el

;;; Steps to reproduce:
;; Put init.el in ~/.emacs.d and thing-thing.el in ~/.emacs.d/lisp
;; Start Emacs
;; Observe that the following message appears:
;;   error: Required feature ‘thing-thing’ was not provided
;; Observe that in the messages buffer, features contained thing-thing after
;;   thing-thing.el finished executing
;; Observe that features now does not contain thing-thing
;; Observe that side-effects of the execution of thing-thing still occurred,
;;   namely the creation of the variable thing-var and the printing to the
;;   messages buffer
;; Observe the alternate form (commented out) works without error

(add-to-list 'load-path "~/.emacs.d/lisp")

(defun symbol-append-thing (sym)
  "Take a symbol and make a new symbol with \"-thing\" appended to it."
  (make-symbol (concat (symbol-name sym) "-thing")))

(mapc 'require (list (symbol-append-thing 'thing)))

; (mapc 'require (list 'thing-thing))

thing-thing.el

(defvar thing-var 12)

(provide 'thing-thing)

(message "%s" features)