My pod install complains I'm using an outdated cocoapods version (1.7.3), even though I have a newer one installed (1.10.1). When I ran gem list, I could see I had two different versions installed.
So I ran gem uninstall cocoapods and uninstalled the outdated version, 1.7.3. Now, pod install just complains I'm missing the old cocoapods version (1.7.3) instead of using the newer version 1.10.1 which I still have installed. Running bundle install just re-installs 1.7.3 again. I also checked pod --version which outputs 1.7.3