herokuにrailsアプリをpushしてreview appを作成したら急に上記エラーが発生しました
Installing dependencies using bundler 2.2.11
Running: BUNDLE_WITHOUT='development:test' BUNDLE_PATH=vendor/bundle BUNDLE_BIN=vendor/bundle/bin BUNDLE_DEPLOYMENT=1 bundle install -j4
Fetching gem metadata from https://rubygems.org/............
Your bundle is locked to mimemagic (0.3.5), but that version could not be found
in any of the sources listed in your Gemfile. If you haven't changed sources,
that means the author of mimemagic (0.3.5) has removed it. You'll need to update
your bundle to a version other than mimemagic (0.3.5) that hasn't been removed
in order to install.
Bundler Output: Fetching gem metadata from https://rubygems.org/............
Your bundle is locked to mimemagic (0.3.5), but that version could not be found
in any of the sources listed in your Gemfile. If you haven't changed sources,
that means the author of mimemagic (0.3.5) has removed it. You'll need to update
your bundle to a version other than mimemagic (0.3.5) that hasn't been removed
in order to install.調べてみたら、どうやらmimemagicというGemが公開停止したらしく、それが原因でEC2とかHerokuとかで落ちてるっぽいです
とりあえずこちらを実行して解決できました
bundle update mimemagic参考記事
[Rails] bundle installがYour bundle is locked to mimemagic (0.3.5)…で落ちる