Installing pip-tools from source gives UnicodeDecodeError

[AbdealiLoKo]

When I install pip-tools with source, it fails with an ascii codec error.
It works if I install it with the wheel.

Environment Versions

1. OS Type CentOS 7
2. Python version: Python 3.6.6
3. pip version: pip 8.1.2 from /usr/lib/python3.6/site-packages (python 3.6)
4. pip-tools version: NA

Steps to replicate

$ docker run -it --rm centos:7 bash
# yum install -y epel-release
...
# yum install -y python36-pip
...
# pip3.6 install --no-binary :all: pip-tools==3.5.0
Collecting pip-tools==3.5.0
  Downloading https://files.pythonhosted.org/packages/38/03/4d9d73e1bb18920cace97b1e39889129fd3aeec9c10cbef462c92dd4531d/pip-tools-3.5.0.tar.gz (96kB)
    100% |################################| 102kB 312kB/s
    Complete output from command python setup.py egg_info:
    Traceback (most recent call last):
      File "<string>", line 1, in <module>
      File "/tmp/pip-build-xhh_fcip/pip-tools/setup.py", line 20, in <module>
        long_description=read_file('README.rst'),
      File "/tmp/pip-build-xhh_fcip/pip-tools/setup.py", line 10, in read_file
        return thefile.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 0xe2 in position 7532: ordinal not in range(128)

    ----------------------------------------
Command "python setup.py egg_info" failed with error code 1 in /tmp/pip-build-xhh_fcip/pip-tools/
You are using pip version 8.1.2, however version 19.1.1 is available.
You should consider upgrading via the 'pip install --upgrade pip' command.

Expected result

Should have installed

Actual result

Failed to install

[atugushev]

FTR, it could be fixed by adding encoding="utf8" to

pip-tools/setup.py

Line 11 in d640739

with open(join(abspath(dirname(__file__)), filename)) as thefile: