I've been 'stupid' enough to update all packages with pip using pip freeze --local | grep -v '^\-e' | cut -d = -f 1 | xargs -n1 pip install -U.
Ever since I get the same error with a lot of python scripts:

/usr/local/lib/python2.7/dist-packages/requests/__init__.py:80: RequestsDependencyWarning: urllib3 (1.22) or chardet (2.3.0) doesn't match a supported version!
RequestsDependencyWarning)

I've googled but did not find anything to solve this so far. Does anyone have a clue?

I'm not able to renew my letsencrypt certificates since certbot gives the same error... :-(

Some more info:
when I run certbot I get this message:

/usr/local/lib/python2.7/dist-packages/requests/__init__.py:80: RequestsDependencyWarning: urllib3 (1.22) or chardet (2.3.0) doesn't match a supported version!
RequestsDependencyWarning)
An unexpected error occurred:
ContextualVersionConflict: (cryptography 1.5.2 (/home/user/.local/lib/python2.7/site-packages), Requirement.parse('cryptography>=2.1.4'), set(['PyOpenSSL', 'pyOpenSSL']))
Please see the logfile '/tmp/tmpMMOhyW' for more details.

Contents of /tmp/tmpMMOhyW:

2018-02-01 08:46:17,192:DEBUG:certbot.log:Exiting abnormally:
Traceback (most recent call last):
File "/usr/local/bin/certbot", line 11, in <module>
sys.exit(main())
File "/usr/local/lib/python2.7/dist-packages/certbot/main.py", line 1203, in main
plugins = plugins_disco.PluginsRegistry.find_all()
File "/usr/local/lib/python2.7/dist-packages/certbot/plugins/disco.py", line 203, in find_all
plugin_ep = PluginEntryPoint(entry_point)
File "/usr/local/lib/python2.7/dist-packages/certbot/plugins/disco.py", line 50, in __init__
self.plugin_cls = entry_point.load()
File "/home/user/.local/lib/python2.7/site-packages/pkg_resources/__init__.py", line 2263, in load
self.require(*args, **kwargs)
File "/home/user/.local/lib/python2.7/site-packages/pkg_resources/__init__.py", line 2280, in require
items = working_set.resolve(reqs, env, installer)
File "/home/user/.local/lib/python2.7/site-packages/pkg_resources/__init__.py", line 861, in resolve
raise VersionConflict(dist, req).with_context(dependent_req)
ContextualVersionConflict: (cryptography 1.5.2 (/home/user/.local/lib/python2.7/site-packages), Requirement.parse('cryptography>=2.1.4'), set(['PyOpenSSL', 'pyOpenSSL']))
2018-02-01 08:46:17,192:ERROR:certbot.log:An unexpected error occurred:


Does anyone have a clue?

Specs:
Python 2.7/Python 3.5/Ubuntu 16.04