安装Theano dependencies时Vagrant up失败，无法获取索引URL

Question

以下是发生的错误：

change from absent to present failed: Execution of '/usr/bin/pip install -q git+git://github.com/Theano/Theano.git' returned 1:   Cannot fetch index base URL http://pypi.python.org/simple/
==> default:   Could not find any downloads that satisfy the requirement numpy>=1.9.1 (from Theano==1.0.1-81.gf2a2df1)
==> default: No distributions at all found for numpy>=1.9.1 (from Theano==1.0.1-81.gf2a2df1)