building around bugs that you know exists but dont know where is also a part of it. Reliability in the face of bugs. The mere existence of bugs isn't enough to call the software buggy, if the outcome is reliable (e.g., a triple module redundancy).
For a silly example, see how Python programs have plenty of bugs, but they still (usually) don't allow for the kind of memory exploits that C programs give you.
You could say that Python is designed around preventing these memory bugs.
