做性能测试时，导入locust类库时，报错ValueError: path is on mount 'E:', start on mount 'C:'

一、报错信息：

Collecting locust
  Using cached https://files.pythonhosted.org/packages/46/2e/18d4e363e76ec8f407ed018594f474d5669b3bca3977c4c664940fff95d5/locust-0.0.tar.gz
Collecting locustio (from locust)
  Using cached https://files.pythonhosted.org/packages/36/2b/804dda84897fcdf273dcead315f74306edbdfdd69cc0302ac0b9667a404b/locustio-0.13.1-py2.py3-none-any.whl
Collecting pyzmq>=16.0.2 (from locustio->locust)
  Using cached https://files.pythonhosted.org/packages/34/c2/0427fb278bdf69020a6ceed1efb527304e562862c65951442e88f7c09b37/pyzmq-18.1.1-cp35-cp35m-win_amd64.whl
Collecting six>=1.10.0 (from locustio->locust)
  Using cached https://files.pythonhosted.org/packages/65/26/32b8464df2a97e6dd1b656ed26b2c194606c16fe163c695a992b36c11cdf/six-1.13.0-py2.py3-none-any.whl
Collecting flask>=0.10.1 (from locustio->locust)
  Using cached https://files.pythonhosted.org/packages/9b/93/628509b8d5dc749656a9641f4caf13540e2cdec85276964ff8f43bbb1d3b/Flask-1.1.1-py2.py3-none-any.whl
Collecting msgpack-python>=0.4.2 (from locustio->locust)
  Downloading https://files.pythonhosted.org/packages/8a/20/6eca772d1a5830336f84aca1d8198e5a3f4715cd1c7fc36d3cc7f7185091/msgpack-python-0.5.6.tar.gz (138kB)
Collecting geventhttpclient-wheels==1.3.1.dev2 (from locustio->locust)
  Downloading https://files.pythonhosted.org/packages/6c/8a/