Installation fails on some systems

[nat-n]

I'm a bit baffled about the root cause, but I have simple reproduction steps and a simple fix.

The issue can be reproduced by running this Dockerfile:

FROM centos:7.5.1804
RUN yum update -y && yum install -y python3
RUN python3 -m pip install --upgrade pip
CMD ["python3", "-m", "pip", "install", "betterproto"]

like: docker run --rm -it $(docker build -q .)

Will produce output like:

Collecting betterproto
  Downloading betterproto-1.2.3.tar.gz (24 kB)
  Installing build dependencies ... done
  Getting requirements to build wheel ... error
  ERROR: Command errored out with exit status 1:
   command: /usr/bin/python3 /usr/local/lib/python3.6/site-packages/pip/_vendor/pep517/_in_process.py get_requires_for_build_wheel /tmp/tmptildjr2u
       cwd: /tmp/pip-install-tgfsl0y5/betterproto
  Complete output (20 lines):
  Traceback (most recent call last):
    File "/usr/local/lib/python3.6/site-packages/pip/_vendor/pep517/_in_process.py", line 280, in <module>
      main()
    File "/usr/local/lib/python3.6/site-packages/pip/_vendor/pep517/_in_process.py", line 263, in main
      json_out['return_val'] = hook(**hook_input['kwargs'])
    File "/usr/local/lib/python3.6/site-packages/pip/_vendor/pep517/_in_process.py", line 114, in get_requires_for_build_wheel
      return hook(config_settings)
    File "/tmp/pip-build-env-eqgnnb9a/overlay/lib/python3.6/site-packages/setuptools/build_meta.py", line 148, in get_requires_for_build_wheel
      config_settings, requirements=['wheel'])
    File "/tmp/pip-build-env-eqgnnb9a/overlay/lib/python3.6/site-packages/setuptools/build_meta.py", line 128, in _get_build_requires
      self.run_setup()
    File "/tmp/pip-build-env-eqgnnb9a/overlay/lib/python3.6/site-packages/setuptools/build_meta.py", line 250, in run_setup
      self).run_setup(setup_script=setup_script)
    File "/tmp/pip-build-env-eqgnnb9a/overlay/lib/python3.6/site-packages/setuptools/build_meta.py", line 143, in run_setup
      exec(compile(code, __file__, 'exec'), locals())
    File "setup.py", line 7, in <module>
      long_description=open("README.md", "r").read(),
    File "/usr/lib64/python3.6/encodings/ascii.py", line 26, in decode
      return codecs.ascii_decode(input, self.errors)[0]
  UnicodeDecodeError: 'ascii' codec can't decode byte 0xc2 in position 11237: ordinal not in range(128)

The issue is that the setup.py reads the README, apparently in ascii mode instead of utf-8 even though it's python 3.6.8 (which doesn't behave this one on macOS for example), and seems to find some non-ascii characters. It's not obvious exactly what's wrong with the readme, but the setup.py if easily fixed by updating line 7 to to force utf-8 like:

long_description=open("README.md", "r", encoding="utf-8").read(),

[boukeversteegh]

It is the Copyright symbol at the end of the page. But let's keep it in utf-8. Good fix!