How to fix Python ValueError:bad marshal data?

Question

Running flexget Python script in Ubuntu, I get an error:

$ flexget series forget "Orange is the new black" s03e01
Traceback (most recent call last):
File "/usr/local/bin/flexget", line 7, in <module>
from flexget import main
File "/usr/local/lib/python2.7/dist-packages/flexget/__init__.py", line 11, in <module>
from flexget.manager import Manager
File "/usr/local/lib/python2.7/dist-packages/flexget/manager.py", line 21, in <module>
from sqlalchemy.ext.declarative import declarative_base
File "/usr/local/lib/python2.7/dist-packages/sqlalchemy/ext/declarative/__init__.py", line 8, in <module>
from .api import declarative_base, synonym_for, comparable_using, 
File "/usr/local/lib/python2.7/dist-packages/sqlalchemy/ext/declarative/api.py", line 11, in <module>
from ...orm import synonym as _orm_synonym, 
File "/usr/local/lib/python2.7/dist-packages/sqlalchemy/orm/__init__.py", line 17, in <module>
from .mapper import (
File "/usr/local/lib/python2.7/dist-packages/sqlalchemy/orm/mapper.py", line 27, in <module>
from . import properties
ValueError: bad marshal data (unknown type code)

Answer 1

If you get that error, the compiled version of the Python module (the .pyc file) is corrupt probably. Gentoo Linux provides python-updater, but in Debian the easier way to fix: just delete the .pyc file. If you don't know the pyc, just delete all of them (as root):

find /usr -name '*.pyc' -delete