python mode problem

[Rusi]

emacs  hanged while doing something in python
Had to kill with killall emacs

Thereafter emacs is misbehaving with python mode

With plain run-python

Python 2.7.10 (default, Oct 14 2015, 16:09:02) 
[GCC 5.2.1 20151010] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> python.el: native completion setup loaded
>>> 

With C-u run-python and using python3

Warning (python): Your 'python-shell-interpreter' doesn't seem to support 
readline, yet 'python-shell-completion-native' was t and "python3" is not part 
of the 'python-shell-completion-native-disabled-interpreters' list.  Native 
completions have been disabled locally. 

Too many interlocking bugs to make a clear bug-report
For now: Where is python mode (or other related) cache?
Because if emacs started with -Q there is no problem

emacs 25 on linux