エラーがっ
[!] `FirebaseAnalytics` requires CocoaPods version `>= 1.10.0`, which is not satisfied by your current version, `1.9.3`.
ERROR: While executing gem … (Gem::FilePermissionError)
You don’t have write permissions for the /usr/bin directory.
以下で入れれました。
sudo gem update -n /usr/local/bin cocoapods
[!] Your project does not explicitly specify the CocoaPods master specs repo. Since CDN is now used as the default, you may safely remove it from your repos directory via `pod repo remove master`. To suppress this warning please add `warn_for_unused_master_specs_repo => false` to your Podfile.
このメッセージが出て、
pod repo remove master
これを実行後、pod updateは特にエラーは無くなった。