https://www.cnblogs.com/qinyan20/p/4221789.html

ruby-2.1.1 - #downloading rubygems-2.2.3
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
  0     0    0     0    0     0      0      0 --:--:--  0:00:01 --:--:--     0curl: (22) The requested URL returned error: 404 Not Found
The requested url does not exist(22): 'http://production.cf.rubygems.org/rubygems/rubygems-2.2.3.tgz'
Checking fallback: ftp://production.cf.rubygems.org/rubygems/rubygems-2.2.3.tgz
Checking fallback: http://www.mirrorservice.org/sites/production.cf.rubygems.org/rubygems/rubygems-2.2.3.tgz
No fallback URL could be found, try increasing timeout with:

    echo "export rvm_max_time_flag=20" >> ~/.rvmrc

There has been an error while trying to fetch rubygems. 
Halting the installation.
Gemset '' does not exist, 'rvm ruby-2.1.1 do rvm gemset create ' first, or append '--create'.

解决代码：

rvm get stable

RVM安装pod 教程：

https://www.cnblogs.com/Evelyn-zn/p/5662967.html

https://www.cnblogs.com/Evelyn-zn/p/5662967.html

：https://www.jianshu.com/p/6d1bc61b11b5