tests/histedit-helpers.sh

py3: replace file() with open() in test-clone.t

While I was here, I made sure we write things correctly in bytes mode.

Differential Revision: https://phab.mercurial-scm.org/D2110

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
}