安装GGCNN时，提示报错
ImportError: No module named skbuild
以为只是简单pip安装skbuild就好了，结果试了下清华、科大、阿里的好几个源都没用
Collecting scikit-build Retrying (Retry(total=4, connect=None, read=None, redirect=None, status=None)) after connection broken by 'ConnectTimeoutError(<urllib3.connection.VerifiedHTTPSConnection object at 0x7f81344da590>, 'Connection to pypi.tuna.tsinghua.edu.cn timed out. (connect timeout=15)')': /simple/scikit-build/ Retrying (Retry(total=3, connect=None, read=None, redirect=None, status=None)) after connection broken by 'ConnectTimeoutError(<urllib3.connection.VerifiedHTTPSConnection object at 0x7f81344da750>, 'Connection to pypi.tuna.tsinghua.edu.cn timed out. (connect timeout=15)')': /simple/scikit-build/ Retrying (Retry(total=2, connect=None, read=None, redirect=None, status=None)) after connection broken by 'ConnectTimeoutError(<urllib3.connection.VerifiedHTTPSConnection object at 0x7f81344da8d0>, 'Connection to pypi.tuna.tsinghua.edu.cn timed out. (connect timeout=15)')': /simple/scikit-build/ Retrying (Retry(total=1, connect=None, read=None, redirect=None, status=None)) after connection broken by 'ConnectTimeoutError(<urllib3.connection.VerifiedHTTPSConnection object at 0x7f81344daa10>, 'Connection to pypi.tuna.tsinghua.edu.cn timed out. (connect timeout=15)')': /simple/scikit-build/ Retrying (Retry(total=0, connect=None, read=None, redirect=None, status=None)) after connection broken by 'ConnectTimeoutError(<urllib3.connection.VerifiedHTTPSConnection object at 0x7f81344dab50>, 'Connection to pypi.tuna.tsinghua.edu.cn timed out. (connect timeout=15)')': /simple/scikit-build/ Could not find a version that satisfies the requirement scikit-build (from versions: ) No matching distribution found for scikit-build
挨个测试，最后发现豆瓣的源可以
pip install scikit-build -i http://pypi.douban.com/simple --trusted-host pypi.douban.com
