在使用fab的時候報錯：
pkg_resources.DistributionNotFound: The 'cryptography>=1.1' distribution was not found and is required by paramiko
語義翻譯：
cryptography 版本過低，需要安裝1.1以上版本；
所以執行：
pip install cryptography
報類似錯誤：
build/temp.linux-x86_64-2.6/_openssl.c:72268: 錯誤：‘_cffi_f_sk_X509_push’未聲明(不在函數內)
build/temp.linux-x86_64-2.6/_openssl.c:72269: 錯誤：‘_cffi_f_sk_X509_value’未聲明(不在函數內)
build/temp.linux-x86_64-2.6/_openssl.c:73004: 錯誤：expected ‘=’, ‘,’, ‘;’, ‘asm’ or ‘__attribute__’ before ‘init_openssl’
所以安裝：
yum install openssl-devel python-devel -y
問題解決～！