gem安装错误

在用gem install **时一直报这个错误，完整的错误信息如下：

Error fetching https://rubygems.org:
	SSL_connect returned=1 errno=0 state=SSLv3 read server certificate B: certificate verify failed (https://rubygems.org/specs.4.8.gz)

后台在Google上找到解决方案：

sudo gem sources -r https://rubygems.org
sudo gem sources -a http://rubygems.org  

貌似意思是将https替换成http，再试了一下，果然可以了，但是安装完后别忘了把它设回来：

sudo gem sources -r http://rubygems.org
sudo gem sources -a https://rubygems.org