try to prevent 'org already installed' error message.

config.org

@@ -1021,7 +1021,17 @@ To keep the subheading structure when archiving, set the properties of the super
 #+end_src
 When moving BAR to archive, it will go to FILENAME.org_archive below the heading FOO.
 [[http://doc.endlessparentheses.com/Var/org-archive-location.html][Other examples]]
+
 ** org
+
+This seems necessary to prevent 'org is already installed' error
+https://github.com/jwiegley/use-package/issues/319
+
+#+begin_src emacs-lisp
+(assq-delete-all 'org package--builtins)'
+(assq-delete-all 'org package--builtin-versions)
+#+end_src
+
 #+BEGIN_SRC emacs-lisp
 (defun my--buffer-prop-set (name value)
   "Set a file property called NAME to VALUE in buffer file.
@@ -1050,7 +1060,8 @@ If the property is already set, replace its value."
       (replace-match ""))))
 
 (use-package org
-  :ensure t 
+  :ensure t
+  :pin gnu
   :mode (("\.org$" . org-mode))
   :diminish org-indent-mode
   :defer 1
@@ -1067,7 +1078,7 @@ If the property is already set, replace its value."
     (set (make-local-variable 'company-backends)
          '(company-capf company-files))
     (add-hook 'completion-at-point-functions 'pcomplete-completions-at-point nil t))
-  
+
   (defun my--org-agenda-files-set ()
     "Sets default agenda files.
 Necessary when updating roam agenda todos."
@@ -1473,7 +1484,7 @@ If nil it defaults to `split-string-default-separators', normally
     :init
     (setq emacsql-sqlite3-binary "P:/Tools/sqlite/sqlite3.exe"
           exec-path (append exec-path '("P:/Tools/sqlite"))))
-  
+
   (use-package org-roam
     :requires emacsql-sqlite3
     :init