Log Message:
py-borgbackup: update to 1.1.15.

Version 1.1.15 (2020-12-25)
---------------------------

Compatibility notes:

- 1.1.15 drops python 3.4 support, minimum requirement is 3.5 now.

Fixes:

- extract:

  - improve exception handling when setting xattrs, #5092.
  - emit a warning message giving the path, xattr key and error message.
  - continue trying to restore other xattrs and bsdflags of the same file
    after an exception with xattr-setting happened.
- export-tar:

  - set tar format to GNU_FORMAT explicitly, #5274
  - fix memory leak with ssh: remote repository, #5568
  - fix potential memory leak with ssh: remote repository with partial extraction
- create: fix --dry-run and --stats coexistence, #5415
- use --timestamp for {utcnow} and {now} if given, #5189

New features:

- create: implement --stdin-mode, --stdin-user and --stdin-group, #5333
- allow appending the files cache filename with BORG_FILES_CACHE_SUFFIX env var

Other changes:

- drop python 3.4 support, minimum requirement is 3.5 now.
- enable using libxxhash instead of bundled xxh64 code
- update llfuse requirements (1.3.8)
- set cython language_level in some files to fix warnings
- allow EIO with warning when trying to hardlink
- PropDict: fail early if internal_dict is not a dict
- update shell completions
- tests / CI

  - add a test for the hashindex corruption bug, #5531 #4829
  - fix spurious failure in test_cache_files, #5438
  - added a github ci workflow
  - reduce testing on travis, no macOS, no py3x-dev, #5467
  - travis: use newer dists, native py on dist
- vagrant:

  - remove jessie and trusty boxes, #5348 #5383
  - pyinstaller 4.0, build on py379
  - binary build on stretch64, #5348
  - remove easy_install based pip installation
- docs:

  - clarify '--one-file-system' for btrfs, #5391
  - add example for excluding content using the --pattern cmd line arg
  - complement the documentation for pattern files and exclude files, #5524
  - made ansible playbook more generic, use package instead of pacman. also
    change state from "latest" to "present".
  - complete documentation on append-only remote repos, #5497
  - internals: rather talk about target size than statistics, #5336
  - new compression algorithm policy, #1633 #5505
  - faq: add a hint on sleeping computer, #5301
  - note requirements for full disk access on macOS Catalina, #5303
  - fix/improve description of borg upgrade hardlink usage, #5518
- modernize 1.1 code:

  - drop code/workarounds only needed to support Python 3.4
  - remove workaround for pre-release py37 argparse bug
  - removed some outdated comments/docstrings
  - requirements: remove some restrictions, lock on current versions