ModuleNotFoundError rust_setuptools using new pip version 20.0.1

[anjali-chadha]

After upgrading my pip dependency to 20.0.1, I am getting ModuleNotFoundError while installing rust_fst using pip.

> pip --version                                                                                                 
pip 20.0.1 from /Users/anjch/opt/anaconda3/lib/python3.7/site-packages/pip (python 3.7)

> pip install rust_fst                                                                                                
Collecting rust_fst
  Downloading rust-fst-0.1.2.tar.gz (8.3 kB)
    ERROR: Command errored out with exit status 1:
     command: /Users/anjch/opt/anaconda3/bin/python -c 'import sys, setuptools, tokenize; sys.argv[0] = '"'"'/private/var/folders/pr/0265q6nd5gd6gf9k0f8shxycv008rp/T/pip-install-yzk_xmqs/rust-fst/setup.py'"'"'; __file__='"'"'/private/var/folders/pr/0265q6nd5gd6gf9k0f8shxycv008rp/T/pip-install-yzk_xmqs/rust-fst/setup.py'"'"';f=getattr(tokenize, '"'"'open'"'"', open)(__file__);code=f.read().replace('"'"'\r\n'"'"', '"'"'\n'"'"');f.close();exec(compile(code, __file__, '"'"'exec'"'"'))' egg_info --egg-base /private/var/folders/pr/0265q6nd5gd6gf9k0f8shxycv008rp/T/pip-install-yzk_xmqs/rust-fst/pip-egg-info
         cwd: /private/var/folders/pr/0265q6nd5gd6gf9k0f8shxycv008rp/T/pip-install-yzk_xmqs/rust-fst/
    Complete output (5 lines):
    Traceback (most recent call last):
      File "<string>", line 1, in <module>
      File "/private/var/folders/pr/0265q6nd5gd6gf9k0f8shxycv008rp/T/pip-install-yzk_xmqs/rust-fst/setup.py", line 3, in <module>
        from rust_setuptools import (build_rust_cmdclass, build_install_lib_cmdclass,
    ModuleNotFoundError: No module named 'rust_setuptools'
    ----------------------------------------
ERROR: Command errored out with exit status 1: python setup.py egg_info Check the logs for full command output.

However, the installation succeeds using older version of pip v 19.3

> pip --version                                                                                               
pip 19.3.1 from /Users/anjch/opt/anaconda3/envs/aws/lib/python3.8/site-packages/pip (python 3.8)
> pip install rust_fst                                                                                              
Collecting rust_fst
  Downloading https://files.pythonhosted.org/packages/23/12/42db4ee067877f1a9be3f4f2c1c70499036c45ab2dd0abb44b329ee66756/rust_fst-0.1.2-py2.py3-none-macosx_10_9_x86_64.whl (858kB)
     |████████████████████████████████| 860kB 863kB/s
Requirement already satisfied: cffi>=1.0.0 in ./opt/anaconda3/envs/aws/lib/python3.8/site-packages (from rust_fst) (1.13.2)
Requirement already satisfied: pycparser in ./opt/anaconda3/envs/aws/lib/python3.8/site-packages (from cffi>=1.0.0->rust_fst) (2.19)
Installing collected packages: rust-fst
Successfully installed rust-fst-0.1.2