This update of python-stestr upadtes it to SLES 15 SP2 level.

update to 2.6.0:

* Base project infrastructure
* Add python 3.8 macOS and windows ci jobs
* Update test\_processor.py
* Update config\_file.py
* Update cli.py
* Remove 3.8 azure pipelines jobs
* Update stestr/scheduler.py
* Update to recent hacking version
* Add Python 3.8 support
* Add --pdb flag to stestr run
* Add unit tests around repo initialize
* Handle empty .stestr directory to initialize
* Update issue templates
* Escape Windows paths
* Stop encoding attachments text
* Remove stray reference to removed short form of --random
* Remove abbreviated option for stestr run --random
* Only use stdlib based unittest runner for py >=3.5
* Handle NoneType timestamps in subunit results
* Add links to translated version README
* Add README\_ja.rst
* Update docs
* Revert to the trimmed stdout usage
* Revert to previous stdout and remove usage modification
* Revert "Add back more of the \_get\_runner() logic"
* Add back more of the \_get\_runner() logic
* Remove unused bits from test runner
* Use StringIO instead of tempfile
* Remove console script entrypoint for the runner
* Add license to package metadata
* Add unit tests for output functions
* Add mailmap file to deduplicate authors list
* Add custom test runner and remove testtools runner dependency
* Fix edge case where there are no test times in output
* Mention IRC channel in README
* Add macOS azure pipelines
* Use Azure DevOps build badge instead of appveyor
* Add Deprecation warning on cli usage with py2.7
* Remove appveyor config
* Install vcpython27 when python.version is 2.7
* Set up CI with Azure Pipelines
* Add release automation for pypi artifacts
* Rework logic for suppress attachments and all attachments
* Add readme note about python 2 eol in readme
* Cap sphinx version <2.0.0 when python2.7
* Add flag to print all attachments for successful tests
* Add skips on windows
* Discover python executable when discover is not used
* Update copyright year
* Use str instead of six.text\_type for python2.7
* Fix pep8 error
* Update stestr/repository/memory.py
* Add support to repositories for storing run metadata
* Use yaml.safe\_load instead of yaml.load
* Take care of 'concurrency is None' case
* Add sanity check unittests
* Use to\_int in both CLI and Python API
* Ensure concurrency is always an int