py3: port string formatting
`skipped` is a set of integer revs here. So cast integers to
strings using %d.
None doesn't cast to an empty string on Python 3. So use '' explicitly.
Differential Revision: https://phab.mercurial-scm.org/D2146
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
}