下载某个ios源码后，控制器进入目录执行pod install：
$ pod install
Analyzing dependencies
[!] The version of CocoaPods used to generate the lockfile (0.39.0) is higher than the version of the current executable (0.35.0). Incompatibility issues may arise.
因此我们需要更新cocoapods，执行下面的命令，但是并没有更新成功。
$ gem update cocoapod
Updating installed gems
Nothing to update
查看当前版本：
$ pod --version
0.35.0
怀疑source地址有变化：
$ gem sources -l
*** CURRENT SOURCES ***
http://ruby.taobao.org/
网上查看，告知taobao服务器已经改为https协议，因此执行如下：
$ gem sources -r http://ruby.taobao.org/
http://ruby.taobao.org/ removed from sources
$ gem sources -a https://ruby.taobao.org/
https://ruby.taobao.org/ added to sources
更新系统，提示没有权限：
$ gem update --system
Updating rubygems-update
Fetching: rubygems-update-2.5.1.gem (100%)
ERROR: While executing gem ... (Gem::FilePermissionError)
You don't have write permissions for the /Library/Ruby/Gems/2.0.0 directory.
使用sudo来执行操作：
$ sudo gem update --system
Updating rubygems-update
Fetching: rubygems-update-2.5.1.gem (100%)
Successfully installed rubygems-update-2.5.1
Parsing documentation for rubygems-update-2.5.1
执行安装:
$ pod setup
Setting up CocoaPods master repo
Setup completed
[!] CocoaPods was not able to update the `master` repo. If this is an unexpected issue and persists you can inspect it running `pod repo update --verbose`
根据提示执行repo更新:
$ pod repo update --verbose
Updating spec repo `master`
$ /usr/bin/git pull --ff-only
From https://github.com/CocoaPods/Specs
a0baa68..9a14a05 master -> origin/master
error: Your local changes to the following files would be overwritten by merge:
CocoaPods-version.yml
Specs/1PasswordExtension/1.0.0/1PasswordExtension.podspec.json
Specs/1PasswordExtension/1.0.1/1PasswordExtension.podspec.json
Specs/AKUTestKit/1.1.2/AKUTestKit.podspec.json
Specs/ALCore
Aborting
Updating a5c6b67..9a14a05
[!] CocoaPods was not able to update the `master` repo. If this is an unexpected issue and persists you can inspect it running `pod repo update --verbose`
master分支还是失败，查看网上建议，先清除缓存
rm -rf ~/.cocoapods/repos/master
再重新运行：
$ pod setup
Setting up CocoaPods master repo
CocoaPods 1.0.0.beta.2 is available.
To update use: `gem install cocoapods --pre`
[!] This is a test version we'd love you to try.
For more information see http://blog.cocoapods.org
and the CHANGELOG for this version http://git.io/BaH8pQ.
Setup completed
最后，到下载的ios工程目录下，执行：
$ pod install
Updating local specs repositories
CocoaPods 1.0.0.beta.2 is available.
To update use: `gem install cocoapods --pre`
[!] This is a test version we'd love you to try.
For more information see http://blog.cocoapods.org
and the CHANGELOG for this version http://git.io/BaH8pQ.
Analyzing dependencies
Downloading dependencies
Installing AFNetworking (2.6.3)
Installing AFOnoResponseSerializer (1.0.0)
Installing DTCoreText (1.6.17)
问题解决了！