ImportError: No module named packages.urllib3.poolmanager
ImportError: cannot import name iter_field_objects
Debian and nowadays even other distros make modifications to the requests
package that don’t play well with packages assuming a normal requests. This
is due to stubbornness on both sides.
See issue #82 and issue #140 for past discussions. You have one option to work
around this, that is, to install vdirsyncer in a virtual environment, see
Manual installation.