Python2.7 pipenv install failed: TypeError: 'encoding' is an invalid keyword argument for this function

[echocho]

Steps to reproduce:

1. mkdir test-install-elasticmock && cd test-install-elasticmock

2. pipenv --two && pipenv shell
   Using /usr/local/bin/python2.7 (2.7.17) to create virtualenv...

3. pipenv install elasticmock

4. Error shows up

Error:  An error occurred while installing elasticmock!
Error text: Collecting elasticmock
  Using cached ElasticMock-1.6.1.tar.gz (13 kB)

DEPRECATION: Python 2.7 reached the end of its life on January 1st, 2020. Please upgrade your Python as Python 2.7 is no longer maintained. pip 21.0 will drop support for Python 2.7 in January 2021. More details about Python 2 support in pip can be found at https://pip.pypa.io/en/latest/development/release-process/#python-2-support pip 21.0 will remove support for this functionality.
    ERROR: Command errored out with exit status 1:
     command: /Users/zzheng/.local/share/virtualenvs/test-install-elasticmock-pvSvxvgZ/bin/python2.7 -c 'import sys, setuptools, tokenize; sys.argv[0] = '"'"'/private/var/folders/sk/9mxz4q1x1pg9xb9vkws028s40000gn/T/pip-install-maD_Va/elasticmock/setup.py'"'"'; __file__='"'"'/private/var/folders/sk/9mxz4q1x1pg9xb9vkws028s40000gn/T/pip-install-maD_Va/elasticmock/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/sk/9mxz4q1x1pg9xb9vkws028s40000gn/T/pip-pip-egg-info-ECi5s2
         cwd: /private/var/folders/sk/9mxz4q1x1pg9xb9vkws028s40000gn/T/pip-install-maD_Va/elasticmock/
    Complete output (5 lines):
    Traceback (most recent call last):
      File "<string>", line 1, in <module>
      File "/private/var/folders/sk/9mxz4q1x1pg9xb9vkws028s40000gn/T/pip-install-maD_Va/elasticmock/setup.py", line 10, in <module>
        with open(path.join(this_directory, 'README.md'), encoding='utf-8') as f:
    TypeError: 'encoding' is an invalid keyword argument for this function
    ----------------------------------------
ERROR: Command errored out with exit status 1: python setup.py egg_info Check the logs for full command output.

This is likely caused by a bug in elasticmock. Report this to its maintainers.

Suggestion:
In python2 open() doesn't not have parameter encoding. Should add from io import open to avoid this error.

[echocho]

Sorry, just realized that older versions don't have this issue.