miniconda创建虚拟环境后，在虚拟环境安装tophat，报错。
Solving environment: failed with initial frozen solve. Retrying with flexible solve.Solving environment: failed with repodata from current_repodata.json, will retry with next repodata source.
另开一个虚拟环境，用Python2，可以正常安装。
conda create -n test python=2 tophat
