py3: do not reimplement Abort.__str__() on Python 2
It isn't necessary on Python 2, and the default implementation should be
better than our BaseException_str() clone.
fixbundle() {
grep -v 'saving bundle' | grep -v 'saved backup' | \
grep -v added | grep -v adding | \
grep -v "unable to find 'e' for patching" | \
grep -v "e: No such file or directory" | \
cat
}