For all people out there who have mulitple python instances running (like me with 2.7 which is needed by seafile/seahub & 3.4 for other things) a little hint:
I needed to upgrade urllib3 & chardet special for python 2.7. That worked like this:
seafile@XXXX:~/seafile-server-latest$ sudo python2.7 -m pip uninstall urllib3
Uninstalling urllib3-1.9.1:
/usr/lib/python2.7/dist-packages/urllib3
/usr/lib/python2.7/dist-packages/urllib3-1.9.1.egg-info
Proceed (y/n)? y
Successfully uninstalled urllib3-1.9.1
seafile@XXXX:~/seafile-server-latest$ sudo python2.7 -m pip install urllib3
Collecting urllib3
Cache entry deserialization failed, entry ignored
Using cached https://files.pythonhosted.org/packages/bd/c9/6fdd990019071a4a32a5e7cb78a1d92c53851ef4f56f62a3486e6a7d8ffb/urllib3-1.23-py2.py3-none-any.whl
Installing collected packages: urllib3
Successfully installed urllib3-1.23
seafile@XXXX:~/seafile-server-latest$ sudo python2.7 -m pip uninstall chardet
Uninstalling chardet-2.3.0:
Would remove:
/usr/lib/python2.7/dist-packages/chardet
/usr/lib/python2.7/dist-packages/chardet-2.3.0.egg-info
Proceed (y/n)? y
Successfully uninstalled chardet-2.3.0
seafile@XXXX:~/seafile-server-latest$ sudo python2.7 -m pip install chardet
Collecting chardet
Using cached https://files.pythonhosted.org/packages/bc/a9/01ffebfb562e4274b6487b4bb1ddec7ca55ec7510b22e4c51f14098443b8/chardet-3.0.4-py2.py3-none-any.whl
Installing collected packages: chardet
Successfully installed chardet-3.0.4
After that and a reboot everything went well.