升级10.11后cocoa pods错误，重新安装遇到的问题

（1）https://ruby.taobao.org/

（2）Q：Operation not permitted - /usr/bin/xcodeproj

A:sudo gem update --system
(3)sudo gem install -V cocoa pods

-->
sudo gem install -n /usr/local/bin cocoapods --pre

/*------------------*/

localhost:~ apple$ gem sources --remove https://rubygems.org/
source https://rubygems.org/ not present in cache

localhost:~ apple$ gem   sources -a http://ruby.taobao.org/ 
Error fetching http://ruby.taobao.org/:
bad response Not Found 404 (http://ruby.taobao.org/specs.4.8.gz)

localhost:~ apple$ gem   sources -a http://ruby.taobao.org/ 
Error fetching http://ruby.taobao.org/:
bad response Not Found 404 (http://ruby.taobao.org/specs.4.8.gz)

localhost:~ apple$ gem   sources -a https://ruby.taobao.org/ 
source https://ruby.taobao.org/ already present in the cache

localhost:~ apple$ gem sources -l 

*** CURRENT SOURCES ***
https://ruby.taobao.org/
localhost:~ apple$ sudo gem install -V cocoapods

ERROR:  While executing gem ... (Errno::EPERM)

    Operation not permitted - /usr/bin/xcodeproj

localhost:~ apple$ sudo gem update --system

Updating rubygems-update

Fetching: rubygems-update-2.6.8.gem (100%)

ERROR:  While executing gem ... (Errno::EPERM)

    Operation not permitted - /usr/bin/update_rubygems

localhost:~ apple$ sudo gem install -n /usr/local/bin cocoapods --pre

...

11 gems installed

localhost:~ apple$ sudo gem install -V cocoa pods

...

1 gem installed

localhost:~ apple$ sudo gem install cocoapods

...

ERROR:  While executing gem ... (Errno::EPERM)

    Operation not permitted - /usr/bin/pod

localhost:~ apple$ /usr/bin/ruby -e "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/install)"
localhost:~ apple$ brew install ruby

localhost:~ apple$ sudo gem install -V cocoa pods

...

ERROR:  While executing gem ... (TypeError)

    no implicit conversion of nil into String

localhost:~ apple$ gem update --system

Updating rubygems-update

Fetching: rubygems-update-2.6.8.gem (100%)

ERROR:  While executing gem ... (Gem::FilePermissionError)

    You don't have write permissions for the /Library/Ruby/Gems/2.0.0 directory.

localhost:~ apple$ sudo gem install cocoapods

ERROR:  While executing gem ... (TypeError)

    no implicit conversion of nil into String

localhost:~ apple$ sudo gem install -n /usr/local/bin cocoapods

ERROR:  While executing gem ... (TypeError)

    no implicit conversion of nil into String

localhost:~ apple$ ruby -v

ruby 2.3.3p222 (2016-11-21 revision 56859) [x86_64-darwin15]

localhost:~ apple$ rvm use 2.3.3 —-default

-bash: rvm: command not found

localhost:~ apple$ sudo gem update --system
...

RubyGems system software updated

localhost:~ apple$ sudo gem install -V cocoa pods
...

17 gems installed

localhost:~ apple$ sudo gem update -V
安装成功