Xcode9.3 cocoapods update失败

升级Xcode9.3之后 cocoapods 更新失败  错误如下：

RuntimeError - [Xcodeproj] Unknown object version./Library/Ruby/Gems/2.3.0/gems/xcodeproj-1.5.4/lib/xcodeproj/project.rb:217:in `initialize_from_file'/Library/Ruby/Gems/2.3.0/gems/xcodeproj-1.5.4/lib/xcodeproj/project.rb:102:in `open'/Library/Ruby/Gems/2.3.0/gems/cocoapods-1.4.0.rc.1/lib/cocoapods/installer/analyzer.rb:907:in `block (2 levels) in inspect_targets_to_integrate'/Library/Ruby/Gems/2.3.0/gems/cocoapods-1.4.0.rc.1/lib/cocoapods/installer/analyzer.rb:906:in `each'/Library/Ruby/Gems/2.3.0/gems/cocoapods-1.4.0.rc.1/lib/cocoapods/installer/analyzer.rb:906:in `block in inspect_targets_to_integrate'/Library/Ruby/Gems/2.3.0/gems/cocoapods-1.4.0.rc.1/lib/cocoapods/user_interface.rb:64:in `section'/Library/Ruby/Gems/2.3.0/gems/cocoapods-1.4.0.rc.1/lib/cocoapods/installer/analyzer.rb:901:in `inspect_targets_to_integrate'/Library/Ruby/Gems/2.3.0/gems/cocoapods-1.4.0.rc.1/lib/cocoapods/installer/analyzer.rb:75:in `analyze'/Library/Ruby/Gems/2.3.0/gems/cocoapods-1.4.0.rc.1/lib/cocoapods/installer.rb:243:in `analyze'/Library/Ruby/Gems/2.3.0/gems/cocoapods-1.4.0.rc.1/lib/cocoapods/installer.rb:154:in `block in resolve_dependencies'/Library/Ruby/Gems/2.3.0/gems/cocoapods-1.4.0.rc.1/lib/cocoapods/user_interface.rb:64:in `section'/Library/Ruby/Gems/2.3.0/gems/cocoapods-1.4.0.rc.1/lib/cocoapods/installer.rb:153:in `resolve_dependencies'/Library/Ruby/Gems/2.3.0/gems/cocoapods-1.4.0.rc.1/lib/cocoapods/installer.rb:116:in `install!'/Library/Ruby/Gems/2.3.0/gems/cocoapods-1.4.0.rc.1/lib/cocoapods/command/install.rb:41:in `run'/Library/Ruby/Gems/2.3.0/gems/claide-1.0.2/lib/claide/command.rb:334:in `run'/Library/Ruby/Gems/2.3.0/gems/cocoapods-1.4.0.rc.1/lib/cocoapods/command.rb:52:in `run'/Library/Ruby/Gems/2.3.0/gems/cocoapods-1.4.0.rc.1/bin/pod:55:in `'

解决方案：

升级cocoapods：gem install cocoapods --pre

如果未解决：

这里的Project Format 默认为Xcode 9.3-compatible，将它修改9.3以下即可。