core: Not initializing homekit_controller because could not install requirement homekit==0.12.0

Home Assistant release with the issue: 0.85.0/0.85.1

**Last working Home Assistant release: ** 0.84.x

Operating environment (Hass.io/Docker/Windows/etc.): Debian 9.6 Python VirtualEnv

**Component/platform: ** HomeKit

Description of problem: Since upgrading to 0.85 I’ve been unable to use the HomeKit controller. Digging into the logs today, I see this:

2019-01-15 09:30:35 ERROR (MainThread) [homeassistant.requirements] Not initializing homekit_controller because could not install requirement homekit==0.12.0
2019-01-15 09:30:35 ERROR (MainThread) [homeassistant.setup] Setup failed for homekit_controller: Could not install all requirements.

Digging further, I found the following problem where I’m unable to install the latest HomeKit 0.12 dependancy:

(homeassistant) ha@ha:~$ pip3 --no-cache-dir install homekit==0.12.0
Collecting homekit==0.12.0
  Downloading https://files.pythonhosted.org/packages/1d/a5/f7cb393652053ad3a40f503f1b3f444c56b2f30dfcea913beccfcace7220/homekit-0.12.0.tar.gz (56kB)
    100% |################################| 61kB 2.6MB/s
    Complete output from command python setup.py egg_info:
    Traceback (most recent call last):
      File "<string>", line 1, in <module>
      File "/tmp/pip-install-q0ru5r5i/homekit/setup.py", line 21, in <module>
        long_description = fh.read()
      File "/usr/lib/python3.5/encodings/ascii.py", line 26, in decode
        return codecs.ascii_decode(input, self.errors)[0]
    UnicodeDecodeError: 'ascii' codec can't decode byte 0xc3 in position 7967: ordinal not in range(128)

Problem-relevant configuration.yaml entries and (fill out even if it seems unimportant):

# Discover some devices automatically
discovery:
  enable:
    - homekit