Stick with pip 18.1

Collecting pyinstaller==3.4.0 (from -r requirements-dev.txt (line 2))

  Using cached https://files.pythonhosted.org/packages/03/32/0e0de593f129bf1d1e77eed562496d154ef4460fd5cecfd78612ef39a0cc/PyInstaller-3.4.tar.gz
  Installing build dependencies: started
  Installing build dependencies: finished with status 'done'
  Getting requirements to build wheel: started
  Getting requirements to build wheel: finished with status 'error'
  Complete output from command /Users/hudson/tmp/workspace/Drive/Drive-packages/deploy-dir/.pyenv/versions/3.6.7/bin/python /Users/hudson/tmp/workspace/Drive/Drive-packages/deploy-dir/.pyenv/versions/3.6.7/lib/python3.6/site-packages/pip/_vendor/pep517/_in_process.py get_requires_for_build_wheel /tmp/tmpwvkaenk5:

  Traceback (most recent call last):
    File "/Users/hudson/tmp/workspace/Drive/Drive-packages/deploy-dir/.pyenv/versions/3.6.7/lib/python3.6/site-packages/pip/_vendor/pep517/_in_process.py", line 207, in <module>
      main()
    File "/Users/hudson/tmp/workspace/Drive/Drive-packages/deploy-dir/.pyenv/versions/3.6.7/lib/python3.6/site-packages/pip/_vendor/pep517/_in_process.py", line 197, in main
      json_out['return_val'] = hook(**hook_input['kwargs'])
    File "/Users/hudson/tmp/workspace/Drive/Drive-packages/deploy-dir/.pyenv/versions/3.6.7/lib/python3.6/site-packages/pip/_vendor/pep517/_in_process.py", line 54, in get_requires_for_build_wheel
      return hook(config_settings)
    File "/private/tmp/pip-build-env-tfklzbhr/overlay/lib/python3.6/site-packages/setuptools/build_meta.py", line 115, in get_requires_for_build_wheel
      return _get_build_requires(config_settings, requirements=['wheel'])

    File "/private/tmp/pip-build-env-tfklzbhr/overlay/lib/python3.6/site-packages/setuptools/build_meta.py", line 101, in _get_build_requires
      _run_setup()
    File "/private/tmp/pip-build-env-tfklzbhr/overlay/lib/python3.6/site-packages/setuptools/build_meta.py", line 85, in _run_setup
      exec(compile(code, __file__, 'exec'), locals())

    File "setup.py", line 20, in <module>
      from PyInstaller import __version__ as version, HOMEPATH, PLATFORM
  ModuleNotFoundError: No module named 'PyInstaller'