pip throws TypeError: parse() got an unexpected keyword argument 'transport_encoding' when trying to install new packages
I had the same problem and what worked for me was updating pip with conda:
conda install pip
It changed my pip from 9.0.1-py36hadba87b_3 to 9.0.1-py36h226ae91_4 and solved issue.
download https://github.com/html5lib/html5lib-python/tree/master/html5lib and overwrite all the files within html5lib folder in your tensorflow environment "envs\tensorflow\Lib\site-packages\html5lib" Then you should be able to run any "pip install" commands after that