Package `emacs-25.1' is unavailable ?

[tangtutu]

Hi author,
Thank you for provide the learning guide !
I'am a newcomer for Emacs, when learning your c-ide guide and i had a problem as following:

Error (use-package): Failed to install projectile: Package emacs-25.1' is unavailable Error (use-package): projectile/:init: Symbol's function definition is void: projectile-global-mode Error (use-package): Cannot load projectile Error (use-package): Failed to install helm-projectile: Package emacs-25.1' is unavailable
Error (use-package): helm-projectile/:init: Symbol's function definition is void: helm-projectile-on
Error (use-package): Cannot load helm-projectile