composerが急に調子が悪くなったので、composer diagnoseで診断した。 すると、下記のようなエラー。 $ composer diagnose Checking platform settings: OK Checking git settings: OK Checking http connectivity to packagist: OK Checking https connectivity to packagist: OK Checking github.com rate limit: OK Checking disk free space: OK Checking pubkeys: FAIL Missing pubkey for tags verification Missing pubkey for dev verification Run composer