pip安装不行就换个方法,直接下源码
wget https://files.pythonhosted.org/packages/bd/19/3eee1893c29beadf488f900176ab7bfa050056b4791f452cb20487c4da26/Appium-Python-Client-2.6.0.tar.gz
tar -xvf Appium-Python-Client-2.6.0.tar.gz
cd Appium-Python-Client-2.6.0
python setup.py install