tests/histedit-helpers.sh

py3: add pycompat.open and replace open() calls

open() requires mode argument as unicodes on Python 3. This patch introduces
pycompat.open() which is inserted to files using transformer and replaces
builtins.open() calls.

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
}