tools or techniques to help avoid mistakes in python/django
Thank you for your answers, I'll check these tools.
I wanted to share with you other ideas (none python/django specific):

Assert conditions in code - but remove from production code.
Run periodic checks on the data (eg. sending email to dev when found unexpected state) - in case a bug slips by it may be detected faster, before more data is corrupt (but alas after some of it is already corrupt).
Make a single bottom-line test (perhaps simulating user input),  that covers most of the program. It may catch exceptions and asserts and is may be easier to maintain than many tests.
What tools or techniques can help avoid bugs, especially silly mistakes such as typos, coding in Python and Django?
I know unit-testing every line of code is the "proper" way, but are there any shortcuts?
I know of pylint, but unfortunately it doesn't check Django ORM named parameters, where a typo can go unnoticed. Is there any tool that can handle this kind of bugs?  
A colleague thought of an idea to gather smart statistics on tokens (for example about named parameters to functions...), and when a once-in-a-code-base token is encountered it is warned as possible typo.
Do you know of any tool that does something similar?