If pip >= 19.0.0 is installed in site-packages, compile_python_requirements fails

[apt-itude]

It succeeds with v18.1, but after upgrading to v19.0.3:

$ pip2 install -U pip
Collecting pip
  Using cached https://files.pythonhosted.org/packages/d8/f3/413bab4ff08e1fc4828dfc59996d721917df8e8583ea85385d51125dceff/pip-19.0.3-py2.py3-none-any.whl
Installing collected packages: pip
  Found existing installation: pip 18.1
    Uninstalling pip-18.1:
      Successfully uninstalled pip-18.1
Successfully installed pip-19.0.3

I see this error:

Traceback (most recent call last):
  File "/Users/athompson/.pyenv/versions/2.7.15/lib/python2.7/runpy.py", line 174, in _run_module_as_main
    "__main__", fname, loader, pkg_name)
  File "/Users/athompson/.pyenv/versions/2.7.15/lib/python2.7/runpy.py", line 72, in _run_code
    exec code in run_globals
  File "../com_apt_itude_rules_pip/tools/compile_pip_requirements.par/__main__.py", line 13, in <module>
  File "../com_apt_itude_rules_pip/tools/compile_pip_requirements.par/pip_click/click/core.py", line 764, in __call__
  File "../com_apt_itude_rules_pip/tools/compile_pip_requirements.par/pip_click/click/core.py", line 717, in main
  File "../com_apt_itude_rules_pip/tools/compile_pip_requirements.par/pip_click/click/core.py", line 956, in invoke
  File "../com_apt_itude_rules_pip/tools/compile_pip_requirements.par/pip_click/click/core.py", line 555, in invoke
  File "../com_apt_itude_rules_pip/tools/compile_pip_requirements.par/pip_pip_tools/piptools/scripts/compile.py", line 130, in cli
  File "../com_apt_itude_rules_pip/tools/compile_pip_requirements.par/pip_pip_tools/piptools/repositories/pypi.py", line 62, in __init__
AttributeError: Values instance has no attribute 'process_dependency_links'