certbot 0.29.1: Requirement.parse issue

[Schamschula (Marius Schamschula)]

Apparently, there is an upstream issue with the certbot 0.29.1 Python stack:

marius$ certbot
Traceback (most recent call last):
  File "/opt/local/bin/certbot", line 6, in <module>
    from pkg_resources import load_entry_point
  File "/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/pkg_resources/__init__.py", line 3126, in <module>
    @_call_aside
  File "/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/pkg_resources/__init__.py", line 3110, in _call_aside
    f(*args, **kwargs)
  File "/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/pkg_resources/__init__.py", line 3139, in _initialize_master_working_set
    working_set = WorkingSet._build_master()
  File "/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/pkg_resources/__init__.py", line 583, in _build_master
    return cls._build_from_requirements(__requires__)
  File "/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/pkg_resources/__init__.py", line 596, in _build_from_requirements
    dists = ws.resolve(reqs, Environment())
  File "/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/pkg_resources/__init__.py", line 789, in resolve
    raise VersionConflict(dist, req).with_context(dependent_req)
pkg_resources.ContextualVersionConflict: (idna 2.8 (/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages), Requirement.parse('idna<2.8,>=2.5'), set(['requests']))

Also see: ​https://community.letsencrypt.org/t/unable-to-issue-certificate/79411/4