I was trying to install Keras on my python 3.6 environment. I created a new virtual environment with python 3.6 using conda/anaconda.
I was able to activate this virtual environment by entering activate tensorfow in the cmd and then type python to enter python shell. However, after installing Keras and its dependencies, I found that I was not able to activate the environment. The prompt showed error messages as the screenshot showes, and then it crashed immediately.

After googling for a while, it turns out that the package vs2015_win-64 is probably the cause of this problem. I delete the package using conda uninstall vs2015_win-64, and all works smoothly now.